Researchers from the University of Michigan identified of 86% of live Tor "bridges" with a single scan?

Tue Oct 11 10:17:46 PDT 2022

2013

Researchers from the [[University of Michigan]] developed a network
scanner allowing identification of 86% of live Tor "bridges" with a
single scan.<ref name="twe-zmap"/>

<ref name="twe-zmap">{{cite
web|url=http://www.techweekeurope.co.uk/news/zmap-internet-scan-zero-day-125374|title=Zmap's
Fast Internet Scan Tool Could Spread Zero Days In
Minutes|last=Judge|first=Peter|date=20 August 2013|website=TechWeek
Europe|url-status=dead|archive-url=https://web.archive.org/web/20130824142042/http://www.techweekeurope.co.uk/news/zmap-internet-scan-zero-day-125374|archive-date=24
August 2013}}</ref>

{{Short description|Free and open-source anonymity network based on
onion routing}}
{{About|the software and anonymity network|the software's
organization|The Tor Project}}
{{Other uses|Tor (disambiguation)}}
{{Pp-pc1}}
{{Use dmy dates|date=January 2020}}
{{Multiple issues|
{{More citations needed|date=December 2021}}
{{Duplication|date=August 2022|dupe=#Bad apple attack}}
{{POV|date=February 2021}}
}}
{{Infobox software
| name = Tor
| logo = [[File:Tor-logo-2011-flat.svg|150px]]
| logo caption = [[The Tor Project]] logo
| screenshot = [[File:Tor November 2021.png|250px]]
| caption = The [[#Tor Browser|Tor Browser]] default homepage
| collapsible =
| developer = [[The Tor Project]]
| released = {{Start date and age|2002|9|20|df=y}}<ref name="prealpha" />
| ver layout = stacked
| discontinued =
| programming language = [[C (programming language)|C]],<ref
name="openhub-tor" /> [[Python programming language|Python]], [[Rust
(programming language)|Rust]]<ref>{{cite web | date=2022|
title=Announcing Arti, a pure-Rust Tor implementation|
url=https://blog.torproject.org/announcing-arti}}</ref>
| operating system = [[Unix-like]], ([[Android operating
system|Android]], [[Linux]], [[BSD]], [[macOS]]), [[Microsoft
Windows]], [[IOS]].
| platform =
| size = {{Nowrap|50–55 MB}}
| language =
| genre = [[Overlay network]], [[mix network]], [[onion routing|onion
router]], [[Anonymity application]]
| license = [[BSD licenses#3-clause license ("BSD License 2.0",
"Revised BSD License", "New BSD License", or "Modified BSD
License")|BSD 3-clause license]]<ref name="LICENSE - Tor">{{cite web
|title=LICENSE – Tor's source code
|url=https://gitweb.torproject.org/tor.git/tree/LICENSE
|access-date=15 May 2018 |website=tor |archive-date=5 November 2018
|archive-url=https://web.archive.org/web/20181105121901/https://gitweb.torproject.org/tor.git/tree/LICENSE
|url-status=live }}</ref>
| website = {{URL|torproject.org}}
}}
{{File sharing sidebar}}

'''Tor''', short for '''The Onion Router''',<ref>{{cite
web|url=https://www.bbc.com/news/technology-29987379|title=Dark net
raids were 'overblown' by police, says Tor
Project|last=Lee|first=Dave|work=[[BBC]]|date=10 November
2014|access-date=18 June 2022}}</ref> is [[free and open-source software]] for
enabling [[Anonymity|anonymous communication]].<ref>{{Cite
journal|last=Schmucker|first=Niklas|title=Web tracking|journal=SNET2
Seminar Paper-Summer Term}}</ref> It directs [[Internet]] traffic
through a free, worldwide, volunteer [[overlay network]], consisting
of more than seven thousand relays,<ref name="torstatus" /> to conceal
a user's location and usage from anyone performing [[Computer and
network surveillance#Network surveillance|network surveillance]] or
[[Traffic analysis#In computer security|traffic analysis]].<ref>{{Cite
journal |last1=McCoy |first=Damon |author2=Kevin Bauer |author3=Dirk
Grunwald |author4=Tadayoshi Kohno |author5=Douglas Sicker
|title=Shining light in dark places: Understanding the Tor network
|journal=International Symposium on Privacy Enhancing Technologies
Symposium}}</ref> Using Tor makes it more difficult to trace a user's
Internet activity. Tor's intended use is to protect the personal
privacy of its users, as well as their freedom and ability to
communicate confidentially through [[IP address]] anonymity using Tor
exit nodes.<ref>{{cite web |title=ABOUT TOR BROWSER {{!}} Tor Project
{{!}} Tor Browser Manual
|url=https://tb-manual.torproject.org/about/#:~:text=Tor%20is%20a%20network%20of,out%20onto%20the%20public%20Internet.
|access-date=2022-04-27 |website=tb-manual.torproject.org}}</ref>

==History==
The core principle of Tor, [[onion routing]], was developed in the
mid-1990s by [[United States Naval Research Laboratory]] employees,
[[mathematician]] [[Paul Syverson]], and [[computer scientist]]s [[G.
Mike Reed|Michael G. Reed]] and David Goldschlag, to protect [[United
States Intelligence Community|American intelligence]] communications
online.<ref name=bw-tor-vs /> Onion routing is implemented by means of
[[encryption]] in the [[application layer]] of the [[communication
protocol]] stack, nested like the layers of an [[onion]]. The [[alpha
version]] of Tor, developed by Syverson and computer scientists
[[Roger Dingledine]] and [[Nick Mathewson]] and then called The Onion
Routing project (which was later given the acronym "Tor"), was
launched on 20 September 2002.<ref name="tor-history">{{cite web
|title=History |url=https://www.torproject.org/about/history/
|website=Tor Project |access-date=5 June 2021}}</ref><ref
name="torproject-faq" /> The first public release occurred a year
later.<ref>{{Cite mailing
list|mailing-list=tor-dev|last=Dingledine|first=Rogert|date=8 October
2003|title=Tor is free|publisher=Tor
Project|url=https://lists.torproject.org/pipermail/tor-dev/2003-October/002185.html|access-date=23
September 2016|archive-date=13 February
2017|archive-url=https://web.archive.org/web/20170213031700/https://lists.torproject.org/pipermail/tor-dev/2003-October/002185.html|url-status=live}}</ref>

{{Anchor|Tor project}}
In 2004, the Naval Research Laboratory released the code for Tor under
a free license, and the [[Electronic Frontier Foundation]] (EFF) began
funding Dingledine and Mathewson to continue its development.<ref
name="tor-history" /> In 2006, Dingledine, Mathewson, and five others
founded [[The Tor Project]], a [[Massachusetts]]-based [[501(c)(3)]]
research-education [[nonprofit organization]] responsible for
maintaining Tor. The EFF acted as The Tor Project's [[Fiscal
sponsorship|fiscal sponsor]] in its early years, and early financial
supporters included the U.S. [[Bureau of Democracy, Human Rights, and
Labor]] and [[International Broadcasting Bureau]], [[Internews]],
[[Human Rights Watch]], the [[University of Cambridge]], [[Google]],
and Netherlands-based [[NLnet|Stichting NLnet]].<ref>{{cite
web|date=2009|title=Tor Project Form 990
2008|url=https://www.torproject.org/about/findoc/2008-TorProject-Form990.pdf|url-status=dead|archive-url=https://web.archive.org/web/20170629102518/https://www.torproject.org/about/findoc/2008-TorProject-Form990.pdf|archive-date=29
June 2017|access-date=30 August 2014|website=Tor
Project}}</ref><ref>{{cite web|date=2010|title=Tor Project Form 990
2009|url=https://www.torproject.org/about/findoc/2009-TorProject-Form990andPC.pdf|url-status=dead|archive-url=https://web.archive.org/web/20170629102506/https://www.torproject.org/about/findoc/2009-TorProject-Form990andPC.pdf|archive-date=29
June 2017|access-date=30 August 2014|website=Tor Project}}</ref>
[[File:Geographies of Tor.png|thumb|A [[cartogram]] illustrating Tor
usage]]

Over the course of its existence, various Tor
[[#Weaknesses|weaknesses]] have been discovered and occasionally
exploited. Attacks against Tor are an active area of academic
research<ref>{{cite web|last=Goodin|first=Dan|date=22 July
2014|title=Tor developers vow to fix bug that can uncloak
users|url=https://arstechnica.com/security/2014/07/tor-developers-vow-to-fix-bug-that-can-uncloak-users/|url-status=live|archive-url=https://web.archive.org/web/20170708090704/https://arstechnica.com/security/2014/07/tor-developers-vow-to-fix-bug-that-can-uncloak-users/|archive-date=8
July 2017|access-date=15 June 2017|website=[[Ars
Technica]]}}</ref><ref>{{cite web|title=Selected Papers in
Anonymity|url=http://freehaven.net/anonbib/#2014|url-status=live|archive-url=https://web.archive.org/web/20180712134223/https://www.freehaven.net/anonbib/#2014|archive-date=12
July 2018|access-date=26 October 2005|website=Free Haven}}</ref> that
is welcomed by The Tor Project itself.<ref>{{cite web|title=Tor
Research Home|url=https://research.torproject.org/|url-status=live|archive-url=https://web.archive.org/web/20180626053025/https://research.torproject.org/|archive-date=26
June 2018|access-date=31 July 2014|publisher=torproject.org}}</ref>

== Usage ==
{{Further|Dark web}}
{{Hidden services 2015}}
{{Hidden services 2016}}

Tor enables its users to surf the Internet, chat and send instant
messages anonymously, and is used by a wide variety of people for both
licit and illicit purposes.<ref>{{Cite magazine |last=Zetter
|first=Kim |date=17 May 2005 |title=Tor Torches Online Tracking
|magazine=Wired
|url=http://archive.wired.com/politics/security/news/2005/05/67542?currentPage=all
|access-date=30 August 2014 |archive-date=26 July 2014
|archive-url=https://web.archive.org/web/20140726025108/http://archive.wired.com/politics/security/news/2005/05/67542?currentPage=all
|url-status=live }}</ref> Tor has, for example, been used by criminal
enterprises, [[hacktivism]] groups, and law enforcement agencies at
cross purposes, sometimes simultaneously;<ref name="cso-black-market"
/><ref name="muckrock-hunting-porn" /> likewise, agencies within the
U.S. government variously fund Tor (the [[United States Department of
State|U.S. State Department]], the National Science Foundation, and –
through the Broadcasting Board of Governors, which itself partially
funded Tor until October 2012 – [[Radio Free Asia]]) and seek to
subvert it.<ref name="guardian-nsa-target" /><ref name="bw-tor-vs" />

Tor is not meant to completely solve the issue of anonymity on the
web. Tor is not designed to completely erase tracking but instead to
reduce the likelihood for sites to trace actions and data back to the
user.<ref>{{cite web |title=Tor: Overview
|url=https://www.torproject.org/about/overview.html.en |website=The
Tor Project |access-date=29 April 2015 |archive-date=6 June 2015
|archive-url=https://web.archive.org/web/20150606002957/https://www.torproject.org/about/overview.html.en
|url-status=live }}</ref>

Tor is also used for illegal activities. These can include privacy
protection or censorship circumvention,<ref name="scm-egyptians" /> as
well as distribution of child abuse content, drug sales, or malware
distribution.<ref name=":1">{{Cite journal |last1=Jardine |first1=Eric
|last2=Lindner |first2=Andrew M. |last3=Owenson |first3=Gareth
|date=2020-12-15 |title=The potential harms of the Tor anonymity
network cluster disproportionately in free countries
|journal=Proceedings of the National Academy of Sciences |language=en
|volume=117 |issue=50 |pages=31716–31721 |doi=10.1073/pnas.2011893117
|issn=0027-8424 |pmid=33257555 |pmc=7749358
|bibcode=2020PNAS..11731716J |doi-access=free }}</ref>

Tor has been described by ''[[The Economist]]'', in relation to
[[Bitcoin]] and [[Silk Road (marketplace)|Silk Road]], as being "a
dark corner of the web".<ref name="economist-bitcoin" /> It has been
targeted by the American [[National Security Agency]] and the British
[[GCHQ]] [[signals intelligence]] agencies, albeit with marginal
success,<ref name="guardian-nsa-target" /> and more successfully by
the British [[National Crime Agency]] in its Operation
Notarise.<ref>{{cite web |last1=Boiten |first1=Eerke
|last2=Hernandez-Castro |first2=Julio |date=28 July 2014 |title=Can
you really be identified on Tor or is that just what the cops want you
to believe? |url=http://phys.org/news/2014-07-tor-cops.html
|website=Phys.org |access-date=31 July 2014 |archive-date=1 February
2019 |archive-url=https://web.archive.org/web/20190201224220/https://phys.org/news/2014-07-tor-cops.html
|url-status=live }}</ref> At the same time, GCHQ has been using a tool
named "Shadowcat" for "end-to-end encrypted access to VPS over SSH
using the Tor network".<ref>{{cite web |date=14 July 2014 |title=JTRIG
Tools and Techniques
|url=https://firstlook.org/theintercept/document/2014/07/14/jtrig-tools-techniques/
|website=[[The Intercept]] |access-date=14 July 2014 |archive-date=14
July 2014 |archive-url=https://web.archive.org/web/20140714224430/https://firstlook.org/theintercept/document/2014/07/14/jtrig-tools-techniques/
|url-status=live }}</ref><ref>{{cite web |date=5 July 2012
|title=Document from an internal GCHQ wiki lists tools and techniques
developed by the Joint Threat Research Intelligence Group
|url=https://www.documentcloud.org/documents/1217406-jtrigall.html#document/p4gz
|access-date=30 July 2014 |website=documentcoud.org |archive-date=8
August 2014 |archive-url=https://web.archive.org/web/20140808040612/https://www.documentcloud.org/documents/1217406-jtrigall.html#document/p4gz
|url-status=live }}</ref> Tor can be used for anonymous defamation,
unauthorized [[news leak]]s of sensitive information, [[copyright
infringement]], distribution of illegal sexual content,<ref
name="bbr-cleaning-up" /><ref name="jones-forensics" /><ref
name="gawker-kiddie-porn" /> selling [[controlled substance]]s,<ref
name="gawker-any-drug" /> weapons, and stolen credit card
numbers,<ref>{{Cite news |last=Steinberg |first=Joseph |date=8 January
2015 |title=How Your Teenage Son or Daughter May Be Buying Heroin
Online |work=Forbes
|url=https://www.forbes.com/sites/josephsteinberg/2015/01/08/how-your-children-can-buy-illegal-drugs-online/
|access-date=6 February 2015 |archive-date=10 February 2015
|archive-url=https://web.archive.org/web/20150210015157/http://www.forbes.com/sites/josephsteinberg/2015/01/08/how-your-children-can-buy-illegal-drugs-online/
|url-status=live }}</ref> [[money laundering]],<ref
name="ars-feds-narcotics" /> bank fraud,<ref>{{cite web |date=5
December 2014 |title=Treasury Dept: Tor a Big Source of Bank Fraud
|url=http://krebsonsecurity.com/2014/12/treasury-dept-tor-a-big-source-of-bank-fraud/
|website=Krebs on Security |access-date=7 December 2014
|archive-date=3 February 2019
|archive-url=https://web.archive.org/web/20190203162229/https://krebsonsecurity.com/2014/12/treasury-dept-tor-a-big-source-of-bank-fraud/
|url-status=live }}</ref> [[credit card fraud]], [[identity theft]]
and the exchange of [[counterfeit currency]];<ref>{{cite web
|last=Farivar |first=Cyrus |date=3 April 2015 |title=How a $3.85 latte
paid for with a fake $100 bill led to counterfeit kingpin's downfall
|url=https://arstechnica.com/tech-policy/2015/04/how-a-3-85-latte-paid-for-with-a-fake-100-bill-lead-to-counterfeit-kingpins-downfall/
|access-date=19 April 2015 |website=Ars Technica |archive-date=18
April 2015 |archive-url=https://web.archive.org/web/20150418023540/http://arstechnica.com/tech-policy/2015/04/how-a-3-85-latte-paid-for-with-a-fake-100-bill-lead-to-counterfeit-kingpins-downfall/
|url-status=live }}</ref> the [[black market]] utilizes the Tor
infrastructure, at least in part, in conjunction with Bitcoin.<ref
name="cso-black-market" /> It has also been used to brick [[Internet
of things|IoT]] devices.<ref name="BrickerBot">{{cite web
|last=Cimpanu |first=Catalin |date=6 April 2017 |title=New Malware
Intentionally Bricks IoT Devices
|url=https://www.bleepingcomputer.com/news/security/new-malware-intentionally-bricks-iot-devices/
|website=BleepingComputer |access-date=7 April 2017 |archive-date=19
February 2019 |archive-url=https://web.archive.org/web/20190219020834/https://www.bleepingcomputer.com/news/security/new-malware-intentionally-bricks-iot-devices/
|url-status=live }}</ref>

In its complaint against [[Ross William Ulbricht]] of [[Silk Road
(marketplace)|Silk Road]], the US [[Federal Bureau of Investigation]]
acknowledged that Tor has "known legitimate uses".<ref
name="compaint-ulbricht" /><ref name="eff-silk-road" /> According to
[[CNET]], Tor's anonymity function is "endorsed by the [[Electronic
Frontier Foundation]] (EFF) and other civil liberties groups as a
method for [[whistleblower]]s and human rights workers to communicate
with journalists".<ref name="cnet-arrested" /> EFF's Surveillance
Self-Defense guide includes a description of where Tor fits in a
larger strategy for protecting privacy and anonymity.<ref
name="eff-ssd-tor" />

In 2014, the EFF's [[Eva Galperin]] told ''[[Businessweek]]'' that
"Tor's biggest problem is press. No one hears about that time someone
wasn't [[stalking|stalked]] by their abuser. They hear how somebody
got away with downloading child porn."<ref name="thecable" />

The Tor Project states that Tor users include "normal people" who wish
to keep their Internet activities private from websites and
advertisers, people concerned about cyber-spying, and users who are
evading censorship such as activists, journalists, and military
professionals. {{As of |2013|11|}}, Tor had about four million
users.<ref>{{Cite news |last=Dredge |first=Stuart |date=5 November
2013 |title=What is Tor? A beginner's guide to the privacy tool
|work=[[The Guardian]]
|url=https://www.theguardian.com/technology/2013/nov/05/tor-beginners-guide-nsa-browser
|access-date=30 August 2014 |archive-date=15 August 2014
|archive-url=https://web.archive.org/web/20140815233728/http://www.theguardian.com/technology/2013/nov/05/tor-beginners-guide-nsa-browser
|url-status=live }}</ref> According to the ''Wall Street Journal'', in
2012 about 14% of Tor's traffic connected from the United States, with
people in "Internet-censoring countries" as its second-largest user
base.<ref>{{Cite news |last=Fowler |first=Geoffrey A. |date=17
December 2012 |title=Tor: An Anonymous, And Controversial, Way to
Web-Surf |work=The Wall Street Journal
|url=https://online.wsj.com/news/articles/SB10001424127887324677204578185382377144280
|access-date=30 August 2014 |archive-date=19 February 2014
|archive-url=https://web.archive.org/web/20140219235003/http://online.wsj.com/news/articles/SB10001424127887324677204578185382377144280
|url-status=live }}</ref> Tor is increasingly used by victims of
[[domestic violence]] and the [[social worker]]s and agencies that
assist them, even though shelter workers may or may not have had
professional training on cyber-security matters.<ref name="Where
Domestic Violence and Cybersecurity Intersect">{{cite web |last=Tveten
|first=Julianne |date=12 April 2017 |title=Where Domestic Violence and
Cybersecurity Intersect
|url=https://rewire.news/article/2017/04/12/domestic-violence-cybersecurity-intersect/
|access-date=9 August 2017 |website=Rewire |archive-date=10 August
2017 |archive-url=https://web.archive.org/web/20170810052253/https://rewire.news/article/2017/04/12/domestic-violence-cybersecurity-intersect/
|url-status=live }}</ref> Properly deployed, however, it precludes
digital stalking, which has increased due to the prevalence of digital
media in contemporary [[online]] life.<ref
name="boston-domestic-abuse" /> Along with [[SecureDrop]], Tor is used
by news organizations such as ''[[The Guardian]]'', ''[[The New
Yorker]]'', [[ProPublica]] and ''[[The Intercept]]'' to protect the
privacy of whistleblowers.<ref>{{Cite news |last=Ellis |first=Justin
|date=5 June 2014 |title=The Guardian introduces SecureDrop for
document leaks |work=Nieman Journalism Lab
|url=http://www.niemanlab.org/2014/06/the-guardian-introduces-securedrop-for-document-leaks/
|access-date=30 August 2014 |archive-date=17 August 2014
|archive-url=https://web.archive.org/web/20140817181552/http://www.niemanlab.org/2014/06/the-guardian-introduces-securedrop-for-document-leaks/
|url-status=live }}</ref>

In March 2015, the [[Parliamentary Office of Science and Technology]]
released a briefing which stated that "There is widespread agreement
that banning online anonymity systems altogether is not seen as an
acceptable policy option in the U.K." and that "Even if it were, there
would be technical challenges." The report further noted that Tor
"plays only a minor role in the online viewing and distribution of
indecent images of children" (due in part to its inherent latency);
its usage by the [[Internet Watch Foundation]], the utility of its
onion services for [[whistleblower]]s, and its circumvention of the
[[Great Firewall]] of China were touted.<ref name="The Daily
Dot">{{cite web |last=O'Neill |first=Patrick Howell |date=9 March 2015
|title=U.K. Parliament says banning Tor is unacceptable and impossible
|url=http://www.dailydot.com/politics/uk-briefing-tor-child-abuse-minor-role/
|access-date=19 April 2015 |website=The Daily Dot |archive-date=2
April 2015 |archive-url=https://web.archive.org/web/20150402091025/http://www.dailydot.com/politics/uk-briefing-tor-child-abuse-minor-role/
|url-status=live }}</ref>

Tor's executive director, Andrew Lewman, also said in August 2014 that
agents of the NSA and the GCHQ have anonymously provided Tor with bug
reports.<ref>{{Cite news |last=Kelion |first=Leo |date=22 August 2014
|title=NSA and GCHQ agents 'leak Tor bugs', alleges developer
|work=BBC News |url=https://www.bbc.com/news/technology-28886462
|access-date=21 July 2018 |archive-date=2 February 2019
|archive-url=https://web.archive.org/web/20190202041855/https://www.bbc.com/news/technology-28886462
|url-status=live }}</ref>

The Tor Project's FAQ offers supporting reasons for the EFF's endorsement:

{{blockquote|Criminals can already do bad things. Since they're
willing to break laws, they already have lots of options available
that provide better privacy than Tor provides...

Tor aims to provide protection for ordinary people who want to follow
the law. Only criminals have privacy right now, and we need to fix
that...

So yes, criminals could in theory use Tor, but they already have
better options, and it seems unlikely that taking Tor away from the
world will stop them from doing their bad things. At the same time,
Tor and other privacy measures can fight identity theft, physical
crimes like stalking, and so on.|source=Tor Project FAQ<ref
name="torproject-faq-abuse" />}}

==Operation==
{{Multiple image
| image1            = How Tor Works 2.svg
| caption1          = [[Infographic]] about how Tor works, by
[[Electronic Frontier Foundation|EFF]]
}}

Tor aims to conceal its users' identities and their online activity
from surveillance and traffic analysis by separating identification
and routing. It is an implementation of [[onion routing]], which
encrypts and then randomly bounces communications through a network of
relays run by volunteers around the globe. These onion routers employ
[[encryption]] in a multi-layered manner (hence the onion metaphor) to
ensure [[perfect forward secrecy]] between relays, thereby providing
users with anonymity in a network location. That anonymity extends to
the hosting of censorship-resistant content by Tor's anonymous onion
service feature.<ref name="usenix-design" /> Furthermore, by keeping
some of the entry relays (bridge relays) secret, users can evade
[[Internet censorship]] that relies upon blocking public Tor
relays.<ref name="torproject-bridges" />

Because the [[IP address]] of the sender and the recipient are not
''both'' in [[cleartext]] at any hop along the way, anyone
eavesdropping at any point along the communication channel cannot
directly identify both ends. Furthermore, to the recipient, it appears
that the last Tor [[Node (networking)|node]] (called the exit node),
rather than the sender, is the originator of the communication.

===Originating traffic===
[[File:EtherApeTorScreenShot.png|thumb|A visual depiction of the
traffic between some Tor relay [[Node (networking)|nodes]] from the
open-source packet sniffing program [[EtherApe]]]]

A Tor user's [[SOCKS]]-aware applications can be configured to direct
their network traffic through a Tor instance's SOCKS interface, which
is listening on TCP port 9050 (for standalone Tor) or 9150 (for Tor
Browser bundle) at [[localhost]].<ref>{{cite web |title=TorPCAP – Tor
Network Forensics
|url=https://www.netresec.com/?page=Blog&month=2018-12&post=TorPCAP---Tor-Network-Forensics
|access-date=12 December 2018 |website=Netresec |date = 12 December
2018|archive-date=12 December 2018
|archive-url=https://web.archive.org/web/20181212201750/https://www.netresec.com/?page=Blog&month=2018-12&post=TorPCAP---Tor-Network-Forensics
|url-status=live }}</ref> Tor periodically creates virtual circuits
through the Tor network through which it can
[[multiplexing|multiplex]] and onion-route that traffic to its
destination. Once inside a Tor network, the traffic is sent from
router to router along the circuit, ultimately reaching an exit node
at which point the [[cleartext]] packet is available and is forwarded
on to its original destination. Viewed from the destination, the
traffic appears to originate at the Tor exit node.

[[File:Tor-non-exit-relay-bandwidth-usage.jpg|thumb|A Tor non-exit
relay with a maximum output of 239.69 kbit/s]]

Tor's application independence sets it apart from most other anonymity
networks: it works at the [[Transmission Control Protocol]] (TCP)
stream level. Applications whose traffic is commonly anonymized using
Tor include [[Internet Relay Chat]] (IRC), [[instant messaging]], and
[[World Wide Web]] browsing.

{{Anchor|Hidden services}}

===Onion services===
{{See also|List of Tor onion services}}
{{Further|Dark web}}

Tor can also provide anonymity to websites and other servers. Servers
configured to receive inbound connections only through Tor are called
'''onion services''' (formerly, '''hidden services''').<ref>{{cite web
|last=Winter |first=Philipp |title=How Do Tor Users Interact With
Onion Services?
|url=https://nymity.ch/onion-services/pdf/sec18-onion-services.pdf
|access-date=27 December 2018 |archive-date=28 December 2018
|archive-url=https://web.archive.org/web/20181228035314/https://nymity.ch/onion-services/pdf/sec18-onion-services.pdf
|url-status=live }}</ref> Rather than revealing a server's IP address
(and thus its network location), an onion service is accessed through
its [[.onion|onion address]], usually via the [[#Tor Browser|Tor
Browser]]. The Tor network understands these addresses by looking up
their corresponding [[public key]]s and ''introduction points'' from a
[[distributed hash table]] within the network. It can route data to
and from onion services, even those hosted behind [[firewall
(computing)|firewalls]] or [[network address translator]]s (NAT),
while preserving the anonymity of both parties. Tor is necessary to
access these onion services.<ref name="torproject-conf-hidden" />

Onion services were first specified in 2003<ref>{{cite web
|last=Mathewson |first=Nick |title=Add first draft of rendezvous point
document |url=https://gitweb.torproject.org/tor.git/commit/?id=3d538f6d702937c23bec33b3bdd62ff9fba9d2a3
|access-date=23 September 2016 |website=Tor Source Code
|archive-date=15 November 2018
|archive-url=https://web.archive.org/web/20181115205018/https://gitweb.torproject.org/tor.git/commit/?id=3d538f6d702937c23bec33b3bdd62ff9fba9d2a3
|url-status=live }}</ref> and have been deployed on the Tor network
since 2004.<ref name="or-locating" /> Other than the database that
stores the onion service descriptors,<ref name="torproject-hidden" />
Tor is decentralized by design; there is no direct readable list of
all onion services, although a number of onion services catalog
publicly known onion addresses.{{Citation needed|date=April 2022}}

Because onion services route their traffic entirely through the Tor
network, connection to an onion service is encrypted end-to-end and
not subject to eavesdropping. There are, however, security issues
involving Tor onion services. For example, services that are reachable
through Tor onion services ''and'' the public Internet are susceptible
to correlation attacks and thus not perfectly hidden. Other pitfalls
include misconfigured services (e.g. identifying information included
by default in web server error responses), uptime and downtime
statistics, intersection attacks, and user error.<ref
name="torproject-hidden" /><ref name="register-embassy-passwd" /> The
[[open-source software|open source]] OnionScan program, written by
independent security researcher [[Sarah Jamie Lewis]], comprehensively
examines onion services for numerous flaws and vulnerabilities.<ref
name="OnionScan">{{cite web |last=Cox |first=Joseph |date=6 April 2016
|title=A Tool to Check If Your Dark Web Site Really Is Anonymous:
'OnionScan' will probe dark web sites for security weaknesses
|url=https://motherboard.vice.com/en_us/article/kb7bg3/onionscan-checks-if-your-dark-web-site-really-is-anonymous
|access-date=7 July 2017 |website=Motherboard |archive-date=16 August
2017 |archive-url=https://web.archive.org/web/20170816012653/https://motherboard.vice.com/en_us/article/kb7bg3/onionscan-checks-if-your-dark-web-site-really-is-anonymous
|url-status=live }}</ref> (Lewis has also pioneered the field of
"Onion Dildonics", [[sex toy]]s which make use of Tor through the
[[Ricochet (software)|Ricochet]] protocol)<ref name="Onion
Dildonics">{{Cite magazine |last=Burgess |first=Matt |date=3 February
2018 |title=Smart Dildos and Vibrators Keep Getting Hacked – But Tor
Could Be the Answer to Safer Connected Sex
|url=https://www.wired.co.uk/article/sex-toy-bluetooth-hacks-security-fix
|magazine=Wired UK |access-date=9 February 2018 |archive-date=9
February 2018 |archive-url=https://web.archive.org/web/20180209182430/https://www.wired.co.uk/article/sex-toy-bluetooth-hacks-security-fix
|url-status=live }}</ref>

Onion services can also be accessed from a standard web browser
without [[client-side]] connection to the Tor network, using services
like [[Tor2web]].<ref>{{Cite magazine |last=Zetter |first=Kim |date=12
December 2008 |title=New Service Makes Tor Anonymized Content
Available to All
|url=https://www.wired.com/threatlevel/2008/12/tor-anonymized/
|magazine=Wired |access-date=22 February 2014 |archive-date=18 March
2014 |archive-url=https://web.archive.org/web/20140318042302/http://www.wired.com/threatlevel/2008/12/tor-anonymized/
|url-status=live }}</ref> Popular sources of [[.onion]] links include
[[Pastebin.com|Pastebin]], [[Twitter]], [[Reddit]], and other
[[Internet forum]]s.<ref>{{Cite news |last=Koebler |first=Jason
|date=23 February 2015 |title=The Closest Thing to a Map of the Dark
Net: Pastebin |work=Motherboard
|url=http://motherboard.vice.com/read/the-closest-thing-to-a-map-of-the-dark-net-pastebin
|access-date=14 July 2015 |archive-date=22 December 2016
|archive-url=https://web.archive.org/web/20161222205738/http://motherboard.vice.com/read/the-closest-thing-to-a-map-of-the-dark-net-pastebin
|url-status=live }}</ref>

===Nyx status monitor===
Nyx (formerly ARM) is a [[Command-line interface|command-line]] status
monitor written in [[Python (programming language)|Python]] for
Tor.<ref>{{cite web |title=Nyx |url=https://nyx.torproject.org/
|website=nyx.torproject.org |language=en |access-date=19 June 2018
|archive-date=26 January 2019
|archive-url=https://web.archive.org/web/20190126070143/https://nyx.torproject.org/
|url-status=live }}</ref><ref>{{cite web |title=Ubuntu Manpage: arm –
Terminal Tor status monitor
|url=http://manpages.ubuntu.com/manpages/precise/man1/arm.1.html
|website=Ubuntu.com |access-date=20 April 2015 |archive-date=20 June
2018 |archive-url=https://web.archive.org/web/20180620002955/http://manpages.ubuntu.com/manpages/precise/man1/arm.1.html
|url-status=live }}</ref> This functions much like [[Top
(software)|top]] does for system usage, providing real time statistics
for:

* resource usage (bandwidth, CPU, and memory usage)
* general relaying information (nickname, fingerprint, flags,
or/dir/controlports)
* event log with optional [[Regular expression|regex]] filtering and
[[Data deduplication|deduplication]]
* connections correlated against Tor's consensus data (IP address,
connection types, relay details, etc.)
* torrc configuration file with [[syntax highlighting]] and validation

Most of Nyx's attributes are configurable through an optional
[[configuration file]]. It runs on any platform supported by [[Curses
(programming library)|curses]] including [[Linux]], [[macOS]], and
other [[Unix-like]] variants.

The project began in the summer of 2009,<ref name="arm introductory
blog posting">{{cite web |title=Summer Conclusion (ARM Project)
|url=https://blog.torproject.org/blog/summer-conclusion-arm-project
|access-date=19 April 2015 |website=torproject.org |archive-date=20
April 2015 |archive-url=https://web.archive.org/web/20150420152618/https://blog.torproject.org/blog/summer-conclusion-arm-project
|url-status=live }}</ref><ref name="arm interview">{{cite web
|title=Interview with Damien Johnson by Brenno Winter
|url=https://www.atagar.com/arm/resources/HFM_INT_0001.mp3
|url-status=dead
|archive-url=https://web.archive.org/web/20141004085010/https://www.atagar.com/arm/resources/HFM_INT_0001.mp3
|archive-date=4 October 2014 |access-date=4 June 2016
|website=atagar.com}}</ref> and since 18 July 2010 it has been an
official part of the Tor Project. It is [[free software]], available
under the [[GNU General Public License]].<ref name=license/>

==Weaknesses==
{{Update|section|date=September 2020}}
Like all current [[latency (engineering)|low-latency]] [[anonymity
network]]s, Tor cannot and does not attempt to protect against
monitoring of traffic at the boundaries of the Tor network (i.e., the
traffic entering and exiting the network). While Tor does provide
protection against [[traffic analysis]], it cannot prevent traffic
confirmation (also called ''end-to-end correlation'').<ref
name="torproject-one-cell" /><ref name="torproject-fail-both-ends" />

A 2009 study{{By whom|date=April 2022}} revealed that Tor and the
alternative network system [[Java Anon Proxy|JonDonym]] (Java Anon
Proxy, JAP) are considered more resilient to website fingerprinting
techniques than other [[tunneling protocol]]s.<ref>{{Cite journal
|last=Herrmann |first=Dominik |last2=Wendolsky |first2=Rolf
|last3=Federrath |first3=Hannes |date=2009 |title=Website
fingerprinting |url=http://dx.doi.org/10.1145/1655008.1655013
|journal=Proceedings of the 2009 ACM workshop on Cloud computing
security - CCSW '09 |location=New York, New York, USA |publisher=ACM
Press |doi=10.1145/1655008.1655013}}</ref>

The reason for this is that conventional single-hop [[VPN]] protocols
do not need to reconstruct packet data nearly as much as a multi-hop
service like Tor or JonDonym. Website fingerprinting yielded greater
than 90% accuracy for identifying [[HTTP]] packets on conventional VPN
protocols versus Tor which yielded only 2.96% accuracy. However, some
protocols like [[OpenSSH]] and [[OpenVPN]] required a large amount of
data before HTTP packets were identified.<ref name="ccsw-attacking" />

Researchers from the [[University of Michigan]] developed a network
scanner allowing identification of 86% of live Tor "bridges" with a
single scan.<ref name="twe-zmap"/>

===Consensus blocking===
Like many decentralized systems, Tor relies on a [[consensus (computer
science)|consensus mechanism]] to periodically update its current
operating parameters, which for Tor are network parameters like which
nodes are good/bad relays, exits, guards, and how much traffic each
can handle. Tor's architecture for deciding the consensus relies on a
small number of directory authority nodes voting on current network
parameters. Currently, there are ten directory authority nodes, and
their health is publicly monitored.<ref>{{cite
web|url=https://consensus-health.torproject.org/ |title=Consensus
health |publisher=Consensus-health.torproject.org |date=
|access-date=2022-03-15}}</ref> The IP addresses of the authority
nodes are [[hard coded]] into each Tor client. The authority nodes
vote every hour to update the consensus, and clients download the most
recent consensus on startup.<ref>{{cite web |title=Getting Started
with Tor Development |author=George Tankersley |date=2017-10-04
|url=https://blog.gtank.cc/tor-dev-101/ |access-date=16 January 2021
|archive-date=22 January 2021
|archive-url=https://web.archive.org/web/20210122001011/https://blog.gtank.cc/tor-dev-101/
|url-status=live }}</ref><ref>{{cite web
|url=https://blog.torproject.org/introducing-bastet-our-new-directory-authority
|title=Introducing Bastet, Our New Directory Authority |author=tommy
|date=2017-11-02 |publisher=[[The Tor Project]] |access-date=16
January 2021 |archive-date=25 November 2020
|archive-url=https://web.archive.org/web/20201125230425/https://blog.torproject.org/introducing-bastet-our-new-directory-authority
|url-status=live }}</ref><ref>{{cite web |title=10 years of collecting
Tor directory data |author=Karsten Loesing |date=2014-05-15
|url=https://blog.torproject.org/10-years-collecting-tor-directory-data
|publisher=[[The Tor Project]] |access-date=16 January 2021
|archive-date=20 June 2020
|archive-url=https://web.archive.org/web/20200620160219/https://blog.torproject.org/10-years-collecting-tor-directory-data
|url-status=live }}</ref> A network congestion attack, such as a
[[DDoS]], can prevent the consensus nodes from communicating and thus
prevent voting to update the consensus.{{Citation needed|date=April
2022}}

===Eavesdropping===

==== Autonomous system (AS) eavesdropping ====
If the same [[Autonomous system (Internet)|autonomous system]] (AS),
responsible for routing packets at least partly, is present on both
path segments from a client to entry relay and from exit relay to
destination, such an AS can statistically correlate traffic on the
entry and exit segments of the path (i.e. traffic confirmation) and
potentially infer the destination with which the client communicated.
In 2012, LASTor proposed a method to predict a set of potential ASes
on these two segments and then avoid choosing this path during the
path selection algorithm on the client side. In this paper, they also
improve latency by choosing shorter geographical paths between a
client and destination.<ref name="LASTor-2012" />

==== Exit node eavesdropping ====
In September 2007, Dan Egerstad, a Swedish security consultant,
revealed he had intercepted usernames and passwords for email accounts
by operating and monitoring Tor exit nodes.<ref
name="wired-rogue-nodes" /> As Tor cannot encrypt the traffic between
an exit node and the target server, any exit node is in a position to
capture traffic passing through it that does not use [[end-to-end
encryption]] such as [[Secure Sockets Layer]] (SSL) or [[Transport
Layer Security]] (TLS). While this may not inherently breach the
anonymity of the source, traffic intercepted in this way by malicious
Tor exit nodes operators can expose information about the source in
either or both of payload and protocol data.<ref name="sf-tor-hack" />
Furthermore, Egerstad is circumspect about the possible subversion of
Tor by intelligence agencies:<ref name="smh-hack-of-year" />

{{blockquote|If you actually look into where these Tor nodes are
hosted and how big they are, some of these nodes cost thousands of
dollars each month just to host because they're using lots of
bandwidth, they're heavy-duty servers and so on. Who would pay for
this and be anonymous?}}

In October 2019, a Tor researcher revealed that since at least 2017,
there were hundreds of highly suspicious entry, relay, and exit nodes,
run by an unknown group, in an unprecedented scale.<ref
name=":2">{{cite web|title=Someone Is Running Hundreds of Malicious
Servers on the Tor Network and Might Be De-Anonymizing Users
|url=https://gizmodo.com/someone-is-running-hundreds-of-malicious-servers-on-the-1848156630
|access-date=2021-12-05|website=Gizmodo |date=3 December 2021
|language=en-us}}</ref><ref name=":3">{{cite
web|date=2021-12-03|title=A mysterious threat actor is running
hundreds of malicious Tor relays
|url=https://therecord.media/a-mysterious-threat-actor-is-running-hundreds-of-malicious-tor-relays/
|access-date=2021-12-05|website=The Record by Recorded
Future|language=en}}</ref><ref>{{cite web|date=2021-05-10|title=Over
25% Of Tor Exit Relays Spied On Users' Dark Web Activities
|url=https://thehackernews.com/2021/05/over-25-of-tor-exit-relays-are-spying.html
|access-date=2021-12-05 |website=The Hacker News |language=en}}</ref>
It was alleged that this number of servers could pose the risk of a
[[sybil attack]] as it could map Tor users' routes inside the network,
increasing risk of deanonymization.<ref>{{cite web | last1 = Paganini
| first1 = Pierluigi | date = 2021-12-03 | title = KAX17 threat actor
is attempting to deanonymize Tor users running thousands of rogue
relays | url = https://cybersecurityworldconference.com/2021/12/03/kax17-threat-actor-is-attempting-to-deanonymize-tor-users-running-thousands-of-rogue-relays/
| publisher = cybersecurityworldconference.com | archiveurl =
https://web.archive.org/web/20210623001008/https://cybersecurityworldconference.com/category/cyber-security/
| archivedate = 2021-06-23 | url-status = live }}</ref><ref name=":2"
/><ref name=":3" /> At some point there were about 900 nodes running
and by November 2021 about 600 of them were purged.<ref>{{cite web
|last=Koppen |first=Georg |date=9 November 2021|title=[tor-relays]
Recent rejection of relays
|url=https://lists.torproject.org/pipermail/tor-relays/2021-November/019980.html
|access-date=2021-12-05}}</ref><ref name=":2" /><ref name=":3" />
Although described as being a deanonymization attempt, the motives and
the achievements of this possibly on-going event are still
unknown.<ref name=":2" /><ref name=":3" />

==== Internal communication attack ====
In October 2011, a research team from [[ESIEA (university)|ESIEA]]
claimed to have discovered a way to compromise the Tor network by
decrypting communication passing over it.<ref name="thn-compromised"
/><ref name="01-chercheurs" /> The technique they describe requires
creating a map of Tor network nodes, controlling one-third of them,
and then acquiring their encryption [[Key (cryptography)|keys]] and
algorithm [[Random seed|seeds]]. Then, using these known keys and
seeds, they claim the ability to decrypt two encryption layers out of
three. They claim to break the third key by a statistical attack. In
order to redirect Tor traffic to the nodes they controlled, they used
a [[denial-of-service]] attack. A response to this claim has been
published on the official Tor Blog stating these rumors of Tor's
compromise are greatly exaggerated.<ref
name="torproject-rumors-exaggerated" />

===Traffic-analysis attack===
There are two methods of traffic-analysis attack, passive and active.
In the passive traffic-analysis method, the attacker extracts features
from the traffic of a specific flow on one side of the network and
looks for those features on the other side of the network. In the
active traffic-analysis method, the attacker alters the timings of the
packets of a flow according to a specific pattern and looks for that
pattern on the other side of the network; therefore, the attacker can
link the flows in one side to the other side of the network and break
the anonymity of it.{{Failed verification | date = August 2022 |
reason = The reference doesn't generally talk about active and passive
analysis.  It suggests 2 active analyses that match this description,
but didn't say this is the only way active analysis can be done like
this sentence does.  It's questionable that this description is
comprehensively right; see relay early traffic confirmation which is
an active analysis.}}<ref name=":0">{{cite conference | last1=Soltani
| first1=Ramin | last2=Goeckel | first2=Dennis | last3=Towsley |
first3=Don | last4=Houmansadr | first4=Amir | title=2017 51st Asilomar
Conference on Signals, Systems, and Computers | chapter=Towards
provably invisible network flow fingerprints | publisher=IEEE | date =
2017-11-27 | isbn = 978-1-5386-1823-3 | pages = 258–262 | arxiv =
1711.10079 | doi = 10.1109/ACSSC.2017.8335179 | s2cid = 4943955 |
chapter-url = https://arxiv.org/pdf/1711.10079.pdf | archiveurl =
https://web.archive.org/web/20220505002059/https://arxiv.org/pdf/1711.10079.pdf
| archivedate = 2022-05-05 | url-status = live}}</ref> It is shown
that, although timing noise is added to the packets, there are active
traffic analysis methods that are robust against such a noise.{{Verify
source | date = August 2022}}<ref name=":0" />

[[Steven Murdoch]] and George Danezis from [[University of Cambridge]]
presented an article at the 2005 [[Institute of Electrical and
Electronics Engineers|IEEE]] [[Symposium]] on security and privacy on
traffic-analysis techniques that allow adversaries with only a partial
view of the network to infer which nodes are being used to relay the
anonymous streams.<ref name="ieee-low-cost" /> These techniques
greatly reduce the anonymity provided by Tor. Murdoch and Danezis have
also shown that otherwise unrelated streams can be linked back to the
same initiator. This attack, however, fails to reveal the identity of
the original user.<ref name="ieee-low-cost" /> Murdoch has been
working with and has been funded by Tor since 2006.{{Citation
needed|date=April 2022}}

===Tor exit node block===
Operators of Internet sites have the ability to prevent traffic from
Tor exit nodes or to offer reduced functionality for Tor users. For
example, it is not generally possible to edit [[Wikipedia]] when using
Tor or when using an IP address also used by a Tor exit node. The
[[BBC]] blocks the IP addresses of all known Tor exit nodes from its
[[iPlayer]] service, although non-exit relays and bridges are not
blocked.<ref>{{cite web |title=BBC iPlayer Help – Why does BBC iPlayer
think I'm outside the UK?
|url=https://www.bbc.co.uk/iplayer/help/troubleshooting/tv-games-consoles/in_the_uk_message
|url-status=dead
|archive-url=https://web.archive.org/web/20171228212137/https://www.bbc.co.uk/iplayer/help/troubleshooting/tv-games-consoles/in_the_uk_message
|archive-date=28 December 2017 |access-date=10 September 2017
|website=BBC |language=en-GB}}</ref>

===Bad apple attack===
In March 2011, researchers with the Rocquencourt [[French Institute
for Research in Computer Science and Automation]] (''Institut national
de recherche en informatique et en automatique'', INRIA), documented
an attack that is capable of revealing the IP addresses of
[[BitTorrent]] users on the Tor network. The "bad apple attack"
exploits Tor's design and takes advantage of insecure application used
to associate the simultaneous use of a secure application with the IP
address of the Tor user in question. One method of attack depends on
control of an exit node or hijacking tracker responses, while a
secondary attack method is based in part on the statistical
exploitation of [[distributed hash table]] tracking.<ref
name="usenix-bad-apple" /> According to the study:<ref
name="usenix-bad-apple" />

The results presented in the bad apple attack research paper are based
on an attack launched against the Tor network by the authors of the
study. The attack targeted six exit nodes, lasted for twenty-three
days, and revealed a total of 10,000 IP addresses of active Tor users.
This study is significant because it is the first documented attack
designed to target [[Peer-to-peer|P2P]] file-sharing applications on
Tor.<ref name="usenix-bad-apple" /> BitTorrent may generate as much as
40% of all traffic on Tor.<ref name="shining-light" /> Furthermore,
the bad apple attack is effective against insecure use of any
application over Tor, not just BitTorrent.<ref name="usenix-bad-apple"
/>

===Some protocols exposing IP addresses===
{{Duplication|date=August 2022|section=yes|dupe=#Bad apple attack}}
Researchers from the [[French Institute for Research in Computer
Science and Automation]] (INRIA) showed that the Tor dissimulation
technique in [[BitTorrent]] can be bypassed by attackers controlling a
Tor exit node. The study was conducted by monitoring six exit nodes
for a period of twenty-three days. Researches used three [[attack
vector]]s:<ref name="manils-compromising" />
;Inspection of BitTorrent control messages: Tracker announces and
extension protocol handshakes may optionally contain a client [[IP
address]]. Analysis of collected data revealed that 35% and 33% of
messages, respectively, contained addresses of clients.<ref
name="manils-compromising" />{{rp|3}}
;Hijacking trackers' responses: Due to lack of encryption or
authentication in communication between the tracker and peer, typical
[[man-in-the-middle attack]]s allow attackers to determine peer IP
addresses and even verify the distribution of content. Such attacks
work when Tor is used only for tracker communication.<ref
name="manils-compromising" />{{rp|4}}
;Exploiting distributed hash tables (DHT): This attack exploits the
fact that [[distributed hash table]] (DHT) connections through Tor are
impossible, so an attacker is able to reveal a target's IP address by
looking it up in the DHT even if the target uses Tor to connect to
other peers.<ref name="manils-compromising" />{{rp|4–5}}

With these techniques, researchers were able to identify other streams
initiated by users, whose IP addresses were revealed.<ref
name="manils-compromising" />

===Sniper attack===
Jansen ''et al.''., describes a [[DDoS]] attack targeted at the Tor
node software, as well as defenses against that attack and its
variants. The attack works using a colluding client and server, and
filling the queues of the exit node until the node runs out of memory,
and hence can serve no other (genuine) clients. By attacking a
significant proportion of the exit nodes this way, an attacker can
degrade the network and increase the chance of targets using nodes
controlled by the attacker.<ref name="andssy-sniper" />

===Heartbleed bug===
The [[Heartbleed]] [[OpenSSL]] [[Software bug|bug]] disrupted the Tor
network for several days in April 2014 while [[private key]]s were
renewed. The Tor Project recommended Tor relay operators and onion
service operators revoke and generate fresh keys after patching
OpenSSL, but noted Tor relays use two sets of keys and Tor's multi-hop
design minimizes the impact of exploiting a single relay.<ref
name="torproject-openssl-cve" /> Five hundred eighty-six relays later
found to be susceptible to the Heartbleed bug were taken offline as a
precautionary measure.<ref name="ml-rejecting" /><ref
name="torproject-news-20140416" /><ref name="ars-ranks-cut" /><ref
name="tp-blacklisting" />

{{Anchor |Relay early attack}}<!-- there are links here; please don't
move/remove without fixing the links -->

=== Relay early traffic confirmation attack ===
{{Further|CERT Coordination Center#Operation Onymous |Operation
Onymous#Tor 0-day exploit}}
{{POV section|date=February 2021}}

On 30 July 2014, the Tor Project issued the security advisory "relay
early traffic confirmation attack" in which the project discovered a
group of relays that tried to de-anonymize onion service users and
operators.<ref>{{harvp | Dingledine |2014}} "On July 4, 2014 we found
a group of relays that we assume were trying to deanonymize users.
They appear to have been targeting people who operate or access Tor
hidden services."</ref> In summary, the attacking onion service
directory node changed the headers of cells being relayed tagging them
as "relay" or "relay early" cells differently to encode additional
information and sent them back to the requesting user/operator. If the
user's/operator's guard/entry node was also part of the attacking
relays, the attacking relays might be able to capture the IP address
of the user/operator along with the onion service information that the
user/operator was requesting. The attacking relays were stable enough
to be designated as "suitable as hidden service directory" and
"suitable as entry guard"; therefore, both the onion service users and
the onion services might have used those relays as guards and hidden
service directory nodes.<ref name="relay-early-attack">{{cite web
|last=Dingledine |first=Roger |date=30 July 2014 |title=Tor security
advisory: "relay early" traffic confirmation attack
|url=https://blog.torproject.org/tor-security-advisory-relay-early-traffic-confirmation-attack
|publisher=The Tor Project |access-date=9 July 2018 |archive-date=24
May 2019 |archive-url=https://web.archive.org/web/20190524031037/https://blog.torproject.org/tor-security-advisory-relay-early-traffic-confirmation-attack
|url-status=live }}</ref>

The attacking nodes joined the network early in the year on 30 January
and the project removed them on 4 July.<ref name=relay-early-attack />
Although the attack's beginning is unclear, the project implied that
between February and July, IP addresses of onion service users and
operators might have been exposed.<ref>{{harvp | Dingledine |2014}}
"...we assume were trying to deanonymize users. They appear to have
been targeting people who operate or access Tor hidden services...
users who operated or accessed hidden services from early February
through July 4 should assume they were affected... We know the attack
looked for users who fetched hidden service descriptors... The attack
probably also tried to learn who published hidden service descriptors,
which would allow the attackers to learn the location of that hidden
service... Hidden service operators should consider changing the
location of their hidden service."</ref>

The project mentioned the following mitigations besides removing the
attacking relays from the network:

* patched relay software to prevent relays from relaying cells with
"relay early" headers that were not intended.<ref>{{harvp | Dingledine
|2014}} "Relays should upgrade to a recent Tor release (0.2.4.23 or
0.2.5.6-alpha), to close the particular protocol vulnerability the
attackers used..."</ref>
* planned update for users' proxy software so that they could inspect
if they received "relay early" cells from the relays (as they are not
supposed to),<ref>{{harvp | Dingledine |2014}} "For expert users, the
new Tor version warns you in your logs if a relay on your path injects
any relay-early cells: look for the phrase 'Received an inbound
RELAY_EARLY cell'"</ref> along with the settings to connect to just
one guard node instead of selecting randomly from 3 to reduce the
probability of connecting to an attacking relay<ref>{{harvp |
Dingledine |2014}} "Clients that upgrade (once new Tor Browser
releases are ready) will take another step towards limiting the number
of entry guards that are in a position to see their traffic, thus
reducing the damage from future attacks like this one... 3) Put out a
software update that will (once enough clients have upgraded) let us
tell clients to move to using one entry guard rather than three, to
reduce exposure to relays over time."</ref>
* recommended that onion services should consider changing their
locations<ref>{{harvp | Dingledine |2014}} "Hidden service operators
should consider changing the location of their hidden service."</ref>
* reminded users and onion service operators that Tor could not
prevent de-anonymization if the attacker controlled or could listen to
both ends of the Tor circuit, like in this attack.<ref>{{harvp |
Dingledine |2014}} "...but remember that preventing traffic
confirmation in general remains an open research problem."</ref>

In November 2014 there was speculation in the aftermath of [[Operation
Onymous]], resulting in 17 arrests internationally, that a Tor
weakness had been exploited. A representative of [[Europol]] was
secretive about the method used, saying: "''This is something we want
to keep for ourselves. The way we do this, we can't share with the
whole world, because we want to do it again and again and
again.''"<ref name="Wired-2014-11-07">{{Cite magazine |last=Greenberg
|first=Andy |date=7 November 2014 |title=Global Web Crackdown Arrests
17, Seizes Hundreds Of Dark Net Domains
|url=https://www.wired.com/2014/11/operation-onymous-dark-web-arrests
|magazine=Wired |access-date=9 August 2015 |archive-date=9 August 2015
|archive-url=https://web.archive.org/web/20150809113102/http://www.wired.com/2014/11/operation-onymous-dark-web-arrests/
|url-status=live }}</ref>
A [[BBC]] source cited a "technical breakthrough"<ref
name="BBC-2014-11-07">{{Cite news |last=Wakefield |first=Jane |date=7
November 2014 |title=Huge raid to shut down 400-plus dark net sites –
|work=BBC News |url=https://www.bbc.co.uk/news/technology-29950946
|access-date=9 August 2015 |archive-date=21 August 2015
|archive-url=https://web.archive.org/web/20150821232538/http://www.bbc.co.uk/news/technology-29950946
|url-status=live }}</ref>
that allowed tracking physical locations of servers, and the initial
number of infiltrated sites led to the exploit speculation. Andrew
Lewman—a Tor Project representative—downplayed this possibility,
suggesting that execution of more traditional police work was more
likely.<ref name="crisis">{{cite web |last=O'Neill |first=Patrick
Howell |date=7 November 2014 |title=The truth behind Tor's confidence
crisis |website=[[The Daily Dot]]
|url=http://www.dailydot.com/politics/tor-crisis-of-confidence/
|access-date=10 November 2014
|archive-url=https://web.archive.org/web/20141110122301/http://www.dailydot.com/politics/tor-crisis-of-confidence/
|archive-date=10 November 2014 |url-status=live }}</ref><ref>{{cite
web |last=Knight |first=Shawn |date=7 November 2014 |title=Operation
Onymous seizes hundreds of darknet sites, 17 arrested globally
|url=http://www.techspot.com/news/58751-operation-onymous-seizes-hundreds-darknet-sites-17-arrested.html
|access-date=8 November 2014 |website=Techspot |archive-date=8
November 2014 |archive-url=https://web.archive.org/web/20141108205443/http://www.techspot.com/news/58751-operation-onymous-seizes-hundreds-darknet-sites-17-arrested.html
|url-status=live }}</ref>

In November 2015 court documents on the matter<ref
name="Motherboard2015">{{cite web |date=11 November 2015 |title=Court
Docs Show a University Helped FBI Bust Silk Road 2, Child Porn
Suspects |url=http://motherboard.vice.com/read/court-docs-show-a-university-helped-fbi-bust-silk-road-2-child-porn-suspects
|access-date=20 November 2015 |website=Motherboard |archive-date=21
November 2015 |archive-url=https://web.archive.org/web/20151121155246/http://motherboard.vice.com/read/court-docs-show-a-university-helped-fbi-bust-silk-road-2-child-porn-suspects
|url-status=live }}</ref>
addressed concerns about security research ethics<ref
name="tor-blog-FBI">{{cite web |date=11 November 2015 |title=Did the
FBI Pay a University to Attack Tor Users?
|url=https://blog.torproject.org/blog/did-fbi-pay-university-attack-tor-users
|access-date=20 November 2015 |website=torproject.org |archive-date=18
November 2015 |archive-url=https://web.archive.org/web/20151118131446/https://blog.torproject.org/blog/did-fbi-pay-university-attack-tor-users
|url-status=live }}</ref>{{Primary source inline|date=February 2021}}
and the right of not being unreasonably searched as guaranteed by the
US [[Fourth Amendment to the United States Constitution|Fourth
Amendment]].<ref name="net-security-2015">{{cite web |last=Zorz
|first=Zeljka |date=12 November 2015 |title=Tor Project claims FBI
paid university researchers $1m to unmask Tor users
|url=http://www.net-security.org/secworld.php?id=19097 |access-date=20
November 2015 |website=Help Net Security |archive-date=17 November
2015 |archive-url=https://web.archive.org/web/20151117020533/http://www.net-security.org/secworld.php?id=19097
|url-status=live }}</ref>{{Unreliable source?|date=February 2021}}
Moreover, the documents, along with expert
opinions,{{Who|date=February 2021}} may also show the connection
between the network attack and the law enforcement operation
including:

* the search warrant for an administrator of Silkroad 2.0 indicated
that from January 2014 until July, the FBI received information from a
"university-based research institute" with the information being
"reliable IP addresses for Tor and onion services such as SR2" that
led to the identification of "at least another seventeen black markets
on Tor" and "approximately 78 IP addresses that accessed a vendor
[[.onion]] address." One of these IP addresses led to the arrest of
the administrator<ref name=Motherboard2015 />
* the chronology and nature of the attack fitted well with the
operation<ref name=Motherboard2015 />
* a senior researcher of [[International Computer Science Institute]],
part of [[University of California, Berkeley]], said in an interview
that the institute which worked with the FBI was "almost certainly"
[[Carnegie Mellon University]] (CMU),<ref name=Motherboard2015 /> and
this concurred with the Tor Project's assessment<ref name=tor-blog-FBI
/> and with an earlier analysis of [[Edward Felten]], a computer
security professor at [[Princeton University]], about researchers from
CMU's [[CERT/CC]] being involved<ref name="Felton2014">{{cite web
|last=Felten|first= Ed|date=31 July 2014 |title=Why were CERT
researchers attacking Tor? |publisher=Freedom to Tinker, Center for
Information Technology Policy, Princeton University
|url=https://freedom-to-tinker.com/blog/felten/why-were-cert-researchers-attacking-tor/
|access-date=9 July 2018
|archive-url=https://web.archive.org/web/20160905235550/https://freedom-to-tinker.com/blog/felten/why-were-cert-researchers-attacking-tor/
|archive-date=5 September 2016 |url-status=live }}</ref>

In his analysis published on 31 July, besides raising ethical issues,
Felten also questioned the fulfillment of CERT/CC's purposes which
were to prevent attacks, inform the implementers of vulnerabilities,
and eventually inform the public. Because in this case, CERT/CC's
staff did the opposite which was to carry out a large-scale
long-lasting attack, withhold vulnerability information from the
implementers, and withhold the same information from the public.<ref
name=Felton2014 />{{Unreliable source?|date=February 2021}} CERT/CC is
a non-profit, computer security research organization [[Government
spending|publicly funded]] through the [[US federal
government]].{{Citation needed|date=February 2021}}<ref>{{Cite
journal|last=Madnick |first=Stuart |author2=Xitong Li |author3=Nazli
Choucri|date=2009|title=Experiences and challenges with using CERT
data to analyze international cyber security|journal=MIT Sloan
Research Paper}}</ref>

===Mouse fingerprinting===
In March 2016, a security researcher based in [[Barcelona]]
demonstrated laboratory techniques using time measurement via
[[JavaScript]] at the 1-[[millisecond]] level<ref name="Researcher
finds new methods of deanonymizing Tor users">{{cite web |last=Cimpanu
|first=Catalin |date=10 March 2016 |title=Tor Users Can Be Tracked
Based on Their Mouse Movements
|url=http://news.softpedia.com/news/tor-users-can-be-tracked-based-on-their-mouse-movements-501602.shtml
|access-date=11 March 2016 |website=Softpedia |archive-date=11 March
2016 |archive-url=https://web.archive.org/web/20160311122218/http://news.softpedia.com/news/tor-users-can-be-tracked-based-on-their-mouse-movements-501602.shtml
|url-status=live }}</ref> which could potentially identify and
correlate a user's unique [[computer mouse|mouse]] movements, provided
the user has visited the same "fingerprinting" website with both the
Tor browser and a regular browser.{{citation needed|date=November
2020}} This [[proof of concept]] exploits the "time measurement via
JavaScript" issue, which had been an open ticket on the Tor Project
for ten months.<ref name="Open Ticket for Ten Months">{{cite web
|last=Anonymous |date=10 March 2016 |title=Tor Users Can Be Tracked
Based On Their Mouse Movements
|url=http://news.slashdot.org/story/16/03/11/0045203/tor-users-can-be-tracked-based-on-their-mouse-movements
|access-date=11 March 2016 |website=Slashdot |archive-date=12 March
2016 |archive-url=https://web.archive.org/web/20160312071945/http://news.slashdot.org/story/16/03/11/0045203/tor-users-can-be-tracked-based-on-their-mouse-movements
|url-status=live }}</ref>

===Circuit fingerprinting attack===
In 2015, the administrators of [[Agora (online marketplace)|Agora]], a
[[darknet market]], announced they were taking the site offline in
response to a recently discovered security vulnerability in Tor. They
did not say what the vulnerability was, but Wired speculated it was
the "Circuit Fingerprinting Attack" presented at the Usenix security
conference.<ref>{{Cite magazine |last=Greenberg |first=Andy |date=26
August 2015 |title=Agora, the Dark Web's Biggest Drug Market, Is Going
Offline |url=https://www.wired.com/2015/08/agora-dark-webs-biggest-drug-market-going-offline/
|magazine=Wired |access-date=13 September 2016 |archive-date=15 August
2016 |archive-url=https://web.archive.org/web/20160815105345/https://www.wired.com/2015/08/agora-dark-webs-biggest-drug-market-going-offline/
|url-status=live }}</ref><ref>{{cite web |author1=Albert Kwon
|author2=Mashael AlSabah |author3=David Lazar |author4=Marc Dacier
|author5=Srinivas Devadas |date=August 2015 |title=Circuit
Fingerprinting Attacks: Passive Deanonymization of Tor Hidden Services
|url=https://www.usenix.org/system/files/conference/usenixsecurity15/sec15-paper-kwon.pdf
|access-date=14 July 2016 |archive-date=9 April 2016
|archive-url=https://web.archive.org/web/20160409103456/https://www.usenix.org/system/files/conference/usenixsecurity15/sec15-paper-kwon.pdf
|url-status=live }}</ref>

===Volume information===
A study showed "anonymization solutions protect only partially against
target selection that may lead to efficient surveillance" as they
typically "do not hide the volume information necessary to do target
selection".<ref>{{cite web |title=The Economics of Mass Surveillance
and the Questionable Value of Anonymous Communications
|url=http://www.econinfosec.org/archive/weis2006/docs/36.pdf|first1=George|last1=Danezis1|first2=Bettina|last2=Wittneben|via=ecoinfosec.org|access-date=27
April 2022 |archive-date=25 October 2016
|archive-url=https://web.archive.org/web/20161025002654/http://www.econinfosec.org/archive/weis2006/docs/36.pdf
|url-status=live }}</ref>

==Implementations==
{{See also|The Tor Project#Tools|Guardian Project (software)#Projects}}
The main implementation of Tor is written primarily in [[C
(programming language)|C]]<ref name="tor-gitlab-repoanalytics" />

=== Tor Browser ===
<!-- [[Portable Tor]] and [[Tor Browser Bundle]] redirect to this section -->
{{Infobox software
| name = Tor Browser
| screenshot = File:Tor-9.png
| caption = Tor Browser on [[Ubuntu]] showing its start page – about:tor
| developer = Tor Project
| ver layout = stacked
| latest release version = {{Multiple releases
  |branch1=Android
  |version1={{wikidata|property|preferred|references|edit|Q15397253|P348|P400=Q94|P548=Q2804309}}
  |date1={{wikidata|qualifier|preferred|single|Q15397253|P348|P400=Q94|P548=Q2804309|P577}}
  |branch2=Linux
  |version2={{wikidata|property|preferred|references|edit|Q15397253|P348|P400=Q388|P548=Q2804309}}
  |date2={{wikidata|qualifier|preferred|single|Q15397253|P348|P400=Q388|P548=Q2804309|P577}}
  |branch3=macOS
  |version3={{wikidata|property|preferred|references|edit|Q15397253|P348|P400=Q14116|P548=Q2804309}}
  |date3={{wikidata|qualifier|preferred|single|Q15397253|P348|P400=Q14116|P548=Q2804309|P577}}
  |branch4=Windows
  |version4={{wikidata|property|preferred|references|edit|Q15397253|P348|P400=Q1406|P548=Q2804309}}
  |date4={{wikidata|qualifier|preferred|single|Q15397253|P348|P400=Q1406|P548=Q2804309|P577}}
}}
| latest preview version = {{Multiple releases
  |branch1=Android
  |version1={{wikidata|property|preferred|references|edit|Q15397253|P348|P400=Q94|P548=Q51930650}}
  |date1={{wikidata|qualifier|preferred|single|Q15397253|P348|P400=Q94|P548=Q51930650|P577}}
  |branch2=Linux
  |version2={{wikidata|property|preferred|references|edit|Q15397253|P348|P400=Q388|P548=Q51930650}}
  |date2={{wikidata|qualifier|preferred|single|Q15397253|P348|P400=Q388|P548=Q51930650|P577}}
  |branch3=macOS
  |version3={{wikidata|property|preferred|references|edit|Q15397253|P348|P400=Q14116|P548=Q51930650}}
  |date3={{wikidata|qualifier|preferred|single|Q15397253|P348|P400=Q14116|P548=Q51930650|P577}}
  |branch4=Windows
  |version4={{wikidata|property|preferred|references|edit|Q15397253|P348|P400=Q1406|P548=Q51930650}}
  |date4={{wikidata|qualifier|preferred|single|Q15397253|P348|P400=Q1406|P548=Q51930650|P577}}
}}
| repo = {{URL|https://gitweb.torproject.org/tor-browser.git/}}
| engine = [[Gecko (software)|Gecko]]
| operating system = {{flatlist|
* [[Windows XP]] and later
* [[Unix-like]] (inc. [[macOS]])
* [[Android (operating system)|Android]]}}
| size = {{Nowrap|65–90 MB}}
| language = 36 languages<ref>{{cite
web|url=https://www.torproject.org/download/languages/|title=Download
Tor Browser in your language|publisher=[[The Tor Project,
Inc.]]|access-date=7 July 2021}}</ref>
| genre = [[Onion routing]], [[anonymity]], [[web browser]], [[feed reader]]
| license = [[Mozilla Public License]]<ref name="license">{{cite
web|title=Tor Project: FAQ
|url=https://torproject.org/docs/faq.html.en |website=torproject.org
|access-date=31 October 2019 |archive-date=24 March 2019
|archive-url=https://web.archive.org/web/20190324153623/https://www.torproject.org/docs/faq.html.en
|url-status=live}}</ref>
| website = {{URL|torproject.org}}
}}

[[File:Tor Browser icon.svg|90px|thumb|Tor Browser-Logo|left]]

The Tor Browser<ref name="tbb">{{cite web |date=23 June 2014
|title=Tor Browser Bundle
|url=https://www.torproject.org/projects/torbrowser.html.en
|archive-url=https://web.archive.org/web/20140623203436/https://www.torproject.org/projects/torbrowser.html.en
|archive-date=23 June 2014 |access-date=21 May 2017 |website=Tor
Project}}</ref> is the flagship product of the Tor Project. It was
created as the Tor Browser Bundle by [[Steven J. Murdoch]]<ref
name="torproject-corepeople" /> and announced in January 2008.<ref
name="tbbannounce">{{Cite mailing list |last=Murdoch |first=Steven J.
|author-link=Steven J. Murdoch |date=30 January 2008 |title=New Tor
distribution for testing: Tor Browser Bundle |mailing-list=tor-talk
|url=https://lists.torproject.org/pipermail/tor-talk/2008-January/007837.html
|access-date=13 January 2020 |archive-date=5 March 2020
|archive-url=https://web.archive.org/web/20200305015731/https://lists.torproject.org/pipermail/tor-talk/2008-January/007837.html
|url-status=live }}</ref> The Tor Browser consists of a modified
Mozilla [[Firefox]] ESR web browser, the TorButton, TorLauncher,
[[NoScript]] and the Tor proxy.<ref name="tbb-design-document" /><ref
name="wu8-ubuntu-ppa" /> Users can run the Tor Browser from
[[removable media]]. It can operate under [[Microsoft Windows]],
[[macOS]], [[Android (operating system)|Android]] and [[Linux]].<ref
name="lj-portable" />

The default [[search engine]] is [[DuckDuckGo]] (until version 4.5,
[[Startpage.com]] was its default). The Tor Browser automatically
starts Tor background processes and routes traffic through the Tor
network. Upon termination of a session the browser deletes
privacy-sensitive data such as HTTP cookies and the browsing
history.<ref name="wu8-ubuntu-ppa" /> This is effective in reducing
[[web tracking]] and [[canvas fingerprinting]], and it also helps to
prevent creation of a [[filter bubble]].{{citation needed|date=April
2022}}

To allow download from places where accessing the Tor Project URL may
be risky or blocked, a [[GitHub]] repository is maintained with links
for releases hosted in other domains.<ref>{{cite web |date=23
September 2020 |title=This repository contains TorBrowser Releases.
|website=[[GitHub]]
|url=https://github.com/TheTorProject/gettorbrowser |access-date=23
September 2020 |archive-date=23 September 2020
|archive-url=https://web.archive.org/web/20200923155534/https://github.com/TheTorProject/gettorbrowser
|url-status=live }}</ref>

{{Anchor|EgotisticalGiraffe}}

==== Firefox/Tor browser attack ====
In 2011, the [[Law enforcement in the Netherlands|Dutch authority]]
investigating [[child pornography]] discovered the IP address of a Tor
onion service site called "Pedoboard" from an unprotected
administrator's account and gave it to the [[FBI]], who traced it to
Aaron McGrath. After a year of surveillance, the FBI launched
"[[Operation Torpedo]]" which resulted in McGrath's arrest and allowed
them to install their [[Network Investigative Technique]] (NIT)
malware on the servers for retrieving information from the users of
the three onion service sites that McGrath controlled.<ref>{{Cite
magazine |last=Poulsen |first=Kevin |date=8 May 2014 |title=Visit the
Wrong Website, and the FBI Could End Up in Your Computer
|url=https://www.wired.com/2014/08/operation_torpedo/
|magazine=[[Wired (magazine)|Wired]] |access-date=12 March 2017
|archive-date=11 January 2018
|archive-url=https://web.archive.org/web/20180111024650/https://www.wired.com/2014/08/operation_torpedo/
|url-status=live }}</ref> The technique, exploiting a Firefox/Tor
browser's vulnerability that had been patched and targeting users that
had not updated, had a [[Adobe Flash|Flash]] application pinging a
user's IP address directly back to an FBI server,<ref>{{cite web
|date=16 July 2015 |title=Feds bust through huge Tor-hidden child porn
site using questionable malware
|url=https://arstechnica.com/tech-policy/2015/07/feds-bust-through-huge-tor-hidden-child-porn-site-using-questionable-malware/
|website=Ars Technica |access-date=26 July 2018 |archive-date=24 March
2020 |archive-url=https://web.archive.org/web/20200324213851/https://arstechnica.com/tech-policy/2015/07/feds-bust-through-huge-tor-hidden-child-porn-site-using-questionable-malware/
|url-status=live }}</ref><ref>{{cite web |title=FBI Tor busting 227 1
|url=https://www.documentcloud.org/documents/2124281-fbi-tor-busting-227-1.html
|access-date=26 July 2018 |archive-date=2 July 2018
|archive-url=https://web.archive.org/web/20180702204642/https://www.documentcloud.org/documents/2124281-fbi-tor-busting-227-1.html
|url-status=live }}</ref><ref>{{Cite journal |last1=Miller
|first1=Matthew |last2=Stroschein |first2=Joshua |last3=Podhradsky
|first3=Ashley |date=25 May 2016 |title=Reverse Engineering a NIT That
Unmasks Tor Users
|url=https://commons.erau.edu/adfsl/2016/wednesday/10/ |journal=Annual
ADFSL Conference on Digital Forensics, Security and Law
|access-date=26 July 2018 |archive-date=2 July 2018
|archive-url=https://web.archive.org/web/20180702204544/https://commons.erau.edu/adfsl/2016/wednesday/10/
|url-status=live }}</ref><ref>{{Cite magazine |date=16 December 2014
|title=The FBI Used the Web's Favorite Hacking Tool to Unmask Tor
Users |url=https://www.wired.com/2014/12/fbi-metasploit-tor/
|magazine=Wired |access-date=26 July 2018 |archive-date=22 February
2019 |archive-url=https://web.archive.org/web/20190222011924/https://www.wired.com/2014/12/fbi-metasploit-tor/
|url-status=live }}</ref> and resulted in revealing at least 25 US
users as well as numerous users from other countries.<ref
name="WiredDeFoggi">{{Cite magazine |date=27 August 2014
|title=Federal Cybersecurity Director Found Guilty on Child Porn
Charges |url=https://www.wired.com/2014/08/federal-cybersecurity-director-guilty-child-porn-charges/
|magazine=Wired |access-date=26 July 2018 |archive-date=23 February
2019 |archive-url=https://web.archive.org/web/20190223085543/https://www.wired.com/2014/08/federal-cybersecurity-director-guilty-child-porn-charges/
|url-status=live }}</ref> McGrath was sentenced to 20 years in prison
in early 2014, with at least 18 other users including a former Acting
[[United States Department of Health and Human Services|HHS]] Cyber
Security Director being sentenced in subsequent cases.<ref>{{cite web
|date=5 January 2015 |title=Former Acting HHS Cyber Security Director
Sentenced to 25 Years in Prison for Engaging in Child Pornography
Enterprise |url=https://www.justice.gov/opa/pr/former-acting-hhs-cyber-security-director-sentenced-25-years-prison-engaging-child
|url-status=live
|archive-url=https://web.archive.org/web/20180702233127/https://www.justice.gov/opa/pr/former-acting-hhs-cyber-security-director-sentenced-25-years-prison-engaging-child
|archive-date=2 July 2018 |publisher=US Department of
Justice}}</ref><ref>{{cite web |date=17 December 2015 |title=New York
Man Sentenced to Six Years in Prison for Receiving and Accessing Child
Pornography |url=https://www.justice.gov/opa/pr/new-york-man-sentenced-six-years-prison-receiving-and-accessing-child-pornography
|url-status=live
|archive-url=https://web.archive.org/web/20180705062657/https://www.justice.gov/opa/pr/new-york-man-sentenced-six-years-prison-receiving-and-accessing-child-pornography
|archive-date=5 July 2018 |publisher=US Department of Justice}}</ref>

In August 2013 it was discovered<ref>{{Cite
magazine|last=Poulsen|first=Kevin|date=2013-08-05|title=Feds Are
Suspects in New Malware That Attacks Tor
Anonymity|magazine=Wired|url=https://www.wired.com/2013/08/freedom-hosting/|access-date=12
March 2017|archive-date=29 April
2014|archive-url=https://web.archive.org/web/20140429202100/http://www.wired.com/2013/08/freedom-hosting/|url-status=live}}</ref><ref>{{cite
web|last=Krebs|first=Brian|date=2013-08-13|title=Firefox Zero-Day Used
in Child Porn Hunt?|url=https://krebsonsecurity.com/2013/08/firefox-zero-day-used-in-child-porn-hunt/|access-date=2020-12-26|website=Krebs
on Security|archive-date=13 December
2020|archive-url=https://web.archive.org/web/20201213180903/https://krebsonsecurity.com/2013/08/firefox-zero-day-used-in-child-porn-hunt/|url-status=live}}</ref>
that the [[Firefox]] browsers in many older versions of the Tor
Browser Bundle were vulnerable to a JavaScript-deployed [[shellcode]]
attack, as NoScript was not enabled by default.<ref
name="guardian-peeling" /> Attackers used this vulnerability to
extract users' MAC and IP addresses and Windows computer names.<ref
name="iw-info-stealing" /><ref name="wired-feds-are-suspects" /><ref
name="ghowen-fby-analysis" /> News reports linked this to an [[Federal
Bureau of Investigation]] (FBI) operation targeting [[Freedom
Hosting]]'s owner, Eric Eoin Marques, who was arrested on a
provisional extradition warrant issued by a United States' court on 29
July.<ref>{{Cite
news|last=O'Faolain|first=Aodhan|date=2013-08-08|title=Man sought in
US on child porn charges further remanded in custody|newspaper=The
Irish Times|url=https://www.irishtimes.com/news/ireland/irish-news/man-sought-in-us-on-child-porn-charges-further-remanded-in-custody-1.1488624|access-date=2020-12-26|archive-date=9
August 2013|archive-url=https://web.archive.org/web/20130809222019/http://www.irishtimes.com/news/ireland/irish-news/man-sought-in-us-on-child-porn-charges-further-remanded-in-custody-1.1488624|url-status=live}}</ref>
The FBI extradited Marques from Ireland to the state of Maryland on 4
charges: distributing; conspiring to distribute; and advertising
[[child pornography]], as well as aiding and abetting advertising of
child pornography.<ref>[https://www.theguardian.com/us-news/2021/sep/16/man-behind-worlds-biggest-source-of-child-abuse-imagery-is-jailed-for-27-years
Man behind world's biggest source of child abuse imagery is jailed for
27 years], the guardian.com, 2021/09/16</ref> The warrant alleged that
Marques was "the largest facilitator of child porn on the planet".<ref
name="mirror-marques" /><ref name="torproject-old-vulnerable"
/>{{qn|date=December 2016}} The FBI acknowledged the attack in a 12
September 2013 court filing in [[Dublin]];<ref
name="wired-fbi-controlled" /> further technical details from a
training presentation leaked by [[Edward Snowden]] revealed the code
name for the exploit as "EgotisticalGiraffe".<ref
name="guardian-how-nsa" />

=== Tor Messenger ===
{{Infobox software
| name = Tor Messenger
| logo = [[File:Tor-messenger.svg|128px]]
| logo alt =
| screenshot = <!-- Image name is enough -->
| caption =
| author =
| developer = The Tor Project
| released = {{Start date and age|2015|10|29|df=yes}}<ref
name="auto">{{cite web |last=Singh |first=Sukhbir |date=29 October
2015 |title=Tor Messenger Beta: Chat over Tor, Easily
|url=https://blog.torproject.org/blog/tor-messenger-beta-chat-over-tor-easily
|access-date=31 October 2015 |website=The Tor Blog |publisher=The Tor
Project |archive-date=30 October 2015
|archive-url=https://web.archive.org/web/20151030223028/https://blog.torproject.org/blog/tor-messenger-beta-chat-over-tor-easily
|url-status=live }}</ref>
| discontinued = yes
<!-- NOTE: While 0.5.0-beta-1 is a preview release, it is specified in
"latest release version" so that
           it is correctly displayed as the final release.
-->| latest release version = 0.5.0-beta-1
| latest release date = {{Start date and
age|2017|09|28|df=yes}}<ref>{{cite web |last=Singh |first=Sukhbir
|date=28 September 2017 |title=Tor Messenger 0.5.0b1 is released
|url=https://blog.torproject.org/tor-messenger-050b1-released
|access-date=6 October 2017 |website=sukhbir's blog |publisher=The Tor
Project |archive-date=6 October 2017
|archive-url=https://web.archive.org/web/20171006112837/https://blog.torproject.org/tor-messenger-050b1-released
|url-status=live }}</ref><ref name=sunset-tormes>{{cite web
|last=Singh |first=Sukhbir |date=2 April 2018 |title=Sunsetting Tor
Messenger |url=https://blog.torproject.org/sunsetting-tor-messenger
|access-date=9 April 2020 |archive-date=2 April 2020
|archive-url=https://web.archive.org/web/20200402233906/https://blog.torproject.org/sunsetting-tor-messenger
|url-status=live }}</ref>
| repo = https://gitweb.torproject.org/tor-messenger-build.git
| programming language = [[C/C++]], [[JavaScript]], [[Cascading Style
Sheets|CSS]], [[XUL]]
| operating system = {{flatlist|
* [[Windows XP]] and later
* [[Unix-like]] (inc. [[macOS]])}}
| size =
| language = English
| genre =
| license =
| website = {{URL|https://trac.torproject.org/projects/tor/wiki/doc/TorMessenger}}
}}

On 29 October 2015, the Tor Project released Tor Messenger Beta, an
instant messaging program based on [[Instantbird]] with Tor and
[[Off-the-Record Messaging|OTR]] built in and used by default.<ref
name="auto" /> Like [[Pidgin (software)|Pidgin]] and [[Adium]], Tor
Messenger supports multiple different instant messaging protocols;
however, it accomplishes this without relying on ''libpurple'',
implementing all chat protocols in the memory-safe language JavaScript
instead.<ref>{{cite web |date=13 July 2015 |title=Tor Messenger Design
Document |url=https://trac.torproject.org/projects/tor/wiki/doc/TorMessenger/DesignDoc
|access-date=22 November 2015 |website=The Tor Project
|archive-date=22 November 2015
|archive-url=https://web.archive.org/web/20151122170840/https://trac.torproject.org/projects/tor/wiki/doc/TorMessenger/DesignDoc
|url-status=live }}</ref><ref>{{cite web |title=Sunsetting Tor
Messenger {{!}} Tor Project
|url=https://blog.torproject.org/sunsetting-tor-messenger/
|access-date=2022-05-07 |website=blog.torproject.org}}</ref>

According to Lucian Armasu of Toms Hardware, in April 2018, the Tor
Project shut down the Tor Messenger project for three reasons: the
developers of "Instabird" {{sic}} discontinued support for their own
software, limited resources and known metadata problems.<ref>{{cite
web |last=Aemasu |first=Lucian |date=3 April 2018 |title=Tor Project
Shuts Down Development Of Tor Messenger
|url=http://www.tomshardware.com/news/tor-project-ends-tor-messenger,36811.html
|access-date=3 April 2018 |website=Tom's Hardware |language=en}}</ref>
The Tor Messenger developers explained that overcoming any
vulnerabilities discovered in the future would be impossible due to
the project relying on outdated software dependencies.<ref>{{cite web
|last=Sharwood |first=Simon |date=3 April 2018 |title=Tor 'sunsets'
secure Messenger that never exited beta
|url=https://www.theregister.co.uk/2018/04/03/tor_messenger_sunset/
|url-status=live
|archive-url=https://web.archive.org/web/20180715115016/https://www.theregister.co.uk/2018/04/03/tor_messenger_sunset/
|archive-date=15 July 2018 |access-date=2 October 2019 |website=The
Register |language=en}}</ref>

===Tor Phone===
{{See also|Tor Phone}}
In 2016, Tor developer Mike Perry announced a prototype tor-enabled
smartphone bases on [[CopperheadOS]].<ref>{{Cite web |last=Staff
|first=Ars |date=2016-11-22 |title=Tor phone is antidote to Google
"hostility" over Android, says developer
|url=https://arstechnica.com/information-technology/2016/11/tor-phone-prototype-google-hostility-android-open-source/
|access-date=2022-08-13 |website=Ars Technica |language=en-us}}</ref>
It was meant as  a direction for tor on mobile. The project was called
'Mission Improbable'. Copperhead's then lead developer Daniel Micah
welcomed the prototype.

===Third-party applications===
The [[Vuze]] (formerly Azureus) [[BitTorrent]] client,<ref
name="vuze-tor" /> [[Bitmessage]] anonymous messaging system,<ref
name="bitmessage-faq" /> and [[TorChat]] instant messenger include Tor
support. OnionShare allows users to share files using Tor.<ref
name="Hassan2016">{{cite book |last1=Hassan |first1=Nihad
|last2=Hijazi |first2=Rami |title=Data Hiding Techniques in Windows
OS: A Practical Approach to Investigation and Defense |year=2016
|publisher=Syngress |isbn=978-0-12-804496-4 |page=184
|url=https://books.google.com/books?id=sy2lCgAAQBAJ&pg=PA184}}</ref>

[[Guardian Project (software)|The Guardian Project]] is actively
developing a free and open-source suite of applications and firmware
for the [[Android (operating system)|Android operating system]] to
improve the security of mobile communications.<ref
name="guardianproject-about" /> The applications include the
[[ChatSecure]] instant messaging client,<ref
name="guardianproject-chatsecure" /> [[Orbot]] Tor implementation<ref
name="guardianproject-orbot" /> (also available for
iOS),<ref>{{Citation |title=Orbot iOS |date=2022-08-25
|url=https://github.com/guardianproject/orbot-ios |publisher=Guardian
Project |access-date=2022-08-25}}</ref> Orweb (discontinued)
privacy-enhanced mobile browser,<ref name="guardianproject-orweb"
/><ref name="n8fr8">{{cite web |last=n8fr8 |date=30 June 2015
|title=Orfox: Aspiring to bring Tor Browser to Android
|url=https://guardianproject.info/2015/06/30/orfox-aspiring-to-bring-tor-browser-to-android/
|access-date=17 August 2015 |website=guardianproject.info |quote=Our
plan is to actively encourage users to move from Orweb to Orfox, and
stop active development of Orweb, even removing to from the Google
Play Store. |archive-date=13 September 2015
|archive-url=https://web.archive.org/web/20150913130030/https://guardianproject.info/2015/06/30/orfox-aspiring-to-bring-tor-browser-to-android/
|url-status=live }}</ref> Orfox, the mobile counterpart of the Tor
Browser, ProxyMob [[Firefox add-on]],<ref
name="guardianproject-proxymob" /> and ObscuraCam.<ref
name="guardianproject-obscuracam" />

[[Onion Browser]]<ref>[https://mtigas/OnionBrowser/blob/2.X/LICENSE
Endless / Onion Browser License (OBL)]</ref> is open-source,
privacy-enhancing web browser for [[iOS]], which uses Tor.<ref>{{cite
web|title=Tor at the Heart: Onion Browser (and more iOS Tor)
|publisher=The Tor Blog
|url=https://blog.torproject.org/blog/tor-heart-onion-browser-and-more-ios-tor|format=|access-date=|last=|date=|year=|language=|pages=}}</ref>
It is available in the iOS [[App
Store]],<ref>[https://apps.apple.com/en/app/onion-browser/id519296448
Onion Browser on the App Store]</ref> and source code is available on
[[GitHub]].<ref name="github-OnionBro">{{cite
web|title=OnionBrowser/OnionBrowser|periodical=GitHub|url=https://github.com/OnionBrowser/OnionBrowser|format=|access-date=|last=|date=2021-06-30|language=en|pages=}}</ref>

[[Brave (web browser)|Brave]] added support for [[Tor (anonymity
network)|Tor]] in its desktop browser's [[private
browsing|private-browsing]] mode.<ref>{{cite
web|last=Shankland|first=Stephen|title=Brave advances browser privacy
with Tor-powered
tabs|url=https://www.cnet.com/news/brave-advances-browser-privacy-with-tor-powered-tabs/|publisher=CNET|date=28
June 2018|access-date=27 September 2018|archive-date=27 September
2018|archive-url=https://web.archive.org/web/20180927204204/https://www.cnet.com/news/brave-advances-browser-privacy-with-tor-powered-tabs/|url-status=live}}</ref>
Users can switch to Tor-enabled browsing by clicking on the hamburger
menu on the top right corner of the browser.<ref>{{cite
web|last=Brave|date=2020-10-05|title=Brave.com now has its own Tor
Onion Service, providing more users with secure access to
Brave|url=https://brave.com/new-onion-service/|access-date=2021-01-22|website=Brave
Browser|archive-date=6 October
2020|archive-url=https://web.archive.org/web/20201006004823/https://brave.com/new-onion-service/|url-status=live}}</ref>

<gallery>
File:Orbot-logo.svg|Orbot logo
File:Onion Browser Icon 2017.png|Onion Browser logo
File:Onion Browser on iPad.png|Onion Browser on [[iPad]]
File:Onion Browser 2.8.1 on iPhone.png|Onion Browser 2.8.1 on [[iPhone]]
</gallery>

===Security-focused operating systems===
Several [[security-focused operating system]]s make or made extensive
use of Tor. These include [[Hardened Linux From Scratch]], [[Incognito
(operating system)|Incognito]], [[Security-focused operating
system#Liberté Linux|Liberté Linux]], [[Qubes OS]], [[Subgraph
(operating system)|Subgraph]], [[Tails (operating system)|Tails]],
Tor-ramdisk, and [[Whonix]].<ref name="xakep-whole-hog" />

== Reception, impact, and legislation ==
[[File:TorPluggable transports-animation.webm|thumb|A very brief
animated primer on Tor pluggable transports,<ref name="Tor Project:
Pluggable Transports">{{cite web |title=Tor Project: Pluggable
Transports |url=https://www.torproject.org/docs/pluggable-transports.html.en
|access-date=5 August 2016 |website=torproject.org |archive-date=13
August 2016 |archive-url=https://web.archive.org/web/20160813004757/https://www.torproject.org/docs/pluggable-transports.html.en
|url-status=live }}</ref> a method of accessing the anonymity
network.]]

Tor has been praised for providing privacy and anonymity to vulnerable
Internet users such as political activists fearing surveillance and
arrest, ordinary web users seeking to circumvent censorship, and
people who have been threatened with violence or abuse by
stalkers.<ref>{{Cite news |last=Brandom |first=Russell |date=9 May
2014 |title=Domestic violence survivors turn to Tor to escape abusers
|work=The Verge
|url=https://www.theverge.com/2014/5/9/5699600/domestic-violence-survivors-turn-to-tor-to-escape-abusers
|access-date=30 August 2014 |archive-date=2 September 2014
|archive-url=https://web.archive.org/web/20140902093440/http://www.theverge.com/2014/5/9/5699600/domestic-violence-survivors-turn-to-tor-to-escape-abusers
|url-status=live }}</ref><ref>{{Cite news |last=Gurnow |first=Michael
|date=1 July 2014 |title=Seated Between Pablo Escobar and Mahatma
Gandhi: The Sticky Ethics of Anonymity Networks |work=Dissident Voice
|url=http://dissidentvoice.org/2013/06/seated-between-pablo-escobar-and-mahatma-gandhi/
|access-date=17 July 2014 |archive-date=6 October 2014
|archive-url=https://web.archive.org/web/20141006101844/http://dissidentvoice.org/2013/06/seated-between-pablo-escobar-and-mahatma-gandhi/
|url-status=live }}</ref> The U.S. National Security Agency (NSA) has
called Tor "the king of high-secure, low-latency Internet
anonymity",<ref name="guardian-nsa-target" /> and ''[[BusinessWeek]]''
magazine has described it as "perhaps the most effective means of
defeating the online surveillance efforts of intelligence agencies
around the world".<ref name=bw-tor-vs /> Other media have described
Tor as "a sophisticated privacy tool",<ref>{{Cite magazine
|last=Zetter |first=Kim |date=1 June 2010 |title=WikiLeaks Was
Launched With Documents Intercepted From Tor |magazine=Wired
|url=https://www.wired.com/2010/06/wikileaks-documents/
|access-date=30 August 2014 |archive-date=12 August 2014
|archive-url=https://web.archive.org/web/20140812114104/http://www.wired.com/2010/06/wikileaks-documents/
|url-status=live }}</ref> "easy to use"<ref>{{Cite news |last=Lee
|first=Timothy B. |date=10 June 2013 |title=Five ways to stop the NSA
from spying on you |newspaper=[[The Washington Post]]
|url=https://www.washingtonpost.com/blogs/wonkblog/wp/2013/06/10/five-ways-to-stop-the-nsa-from-spying-on-you/
|access-date=30 August 2014 |archive-date=4 October 2014
|archive-url=https://web.archive.org/web/20141004072624/http://www.washingtonpost.com/blogs/wonkblog/wp/2013/06/10/five-ways-to-stop-the-nsa-from-spying-on-you/
|url-status=live }}</ref> and "so secure that even the world's most
sophisticated electronic spies haven't figured out how to crack
it".<ref name="thecable">{{Cite news |last1=Harris |first1=Shane
|last2=Hudson |first2=John |date=4 October 2014 |title=Not Even the
NSA Can Crack the State Department's Favorite Anonymous Service
|work=[[Foreign Policy]]
|url=http://thecable.foreignpolicy.com/posts/2013/10/04/not_even_the_nsa_can_crack_the_state_departments_online_anonymity_tool
|access-date=30 August 2014 |archive-date=20 July 2014
|archive-url=https://web.archive.org/web/20140720045913/http://thecable.foreignpolicy.com/posts/2013/10/04/not_even_the_nsa_can_crack_the_state_departments_online_anonymity_tool
|url-status=live }}</ref>

Advocates for Tor say it supports [[freedom of expression]], including
in countries where the Internet is censored, by protecting the privacy
and anonymity of users. The mathematical underpinnings of Tor lead it
to be characterized as acting "like a piece of [[infrastructure]], and
governments naturally fall into paying for infrastructure they want to
use".<ref>{{cite web |last=Norton |first=Quinn |date=9 December 2014
|title=Clearing the air around Tor
|url=http://pando.com/2014/12/09/clearing-the-air-around-tor/
|website=[[PandoDaily]] |access-date=10 December 2014 |archive-date=25
May 2019 |archive-url=https://web.archive.org/web/20190525115617/https://pando.com/2014/12/09/clearing-the-air-around-tor/
|url-status=live }}</ref>

The project was originally developed on behalf of the U.S.
intelligence community and continues to receive U.S. government
funding, and has been criticized as "more resembl[ing] a spook project
than a tool designed by a culture that values accountability or
transparency".<ref name="pando">{{Cite
news|last=Levine|first=Yasha|date=16 July 2014|title=Almost everyone
involved in developing Tor was (or is) funded by the US
government|work=Pando
Daily|url=http://pando.com/2014/07/16/tor-spooks/|url-status=live|access-date=21
April 2016|archive-url=https://web.archive.org/web/20160411185901/https://pando.com/2014/07/16/tor-spooks/|archive-date=11
April 2016}}</ref> {{as of|2012}}, 80% of The Tor Project's $2M annual
budget came from the [[United States government]], with the [[U.S.
State Department]], the [[Broadcasting Board of Governors]], and the
[[National Science Foundation]] as major contributors,<ref
name="boston-free-speech-tech" /> aiming "to aid democracy advocates
in authoritarian states".<ref name="NDR">{{Cite news|date=3 July
2014|title=NSA targets the
privacy-conscious|work=Panorama|publisher=Norddeutscher
Rundfunk|url=http://daserste.ndr.de/panorama/aktuell/nsa230_page-1.html|url-status=live|access-date=4
July 2014|archive-url=https://web.archive.org/web/20140703215350/http://daserste.ndr.de/panorama/aktuell/nsa230_page-1.html|archive-date=3
July 2014|vauthors=Appelbaum J, Gibson A, Goetz J, Kabisch V, Kampf L,
Ryge L}}</ref> Other public sources of funding include [[DARPA]], the
[[United States Naval Research Laboratory|U.S. Naval Research
Laboratory]], and the [[Government of Sweden]].<ref
name="torproject-sponsors" /><ref name="wsj-anonymous-contraversial"
/> Some have proposed that the government values Tor's commitment to
free speech, and uses the darknet to gather intelligence.<ref>Moore,
Daniel; Rid, Thomas. "Cryptopolitik and the Darknet". Survival.
Feb2016, Vol. 58 Issue 1, p7-38. 32p.</ref>{{Request quotation |
date=July 2018}} Tor also receives funding from [[Non-governmental
organization|NGOs]] including [[Human Rights Watch]], and private
sponsors including [[Reddit]] and [[Google]].<ref>Inc., The Tor
Project,. "Tor: Sponsors". www.torproject.org. Retrieved 28 October
2016.</ref> Dingledine said that the [[United States Department of
Defense]] funds are more similar to a [[research grant]] than a
[[procurement|procurement contract]]. Tor executive director Andrew
Lewman said that even though it accepts funds from the U.S. federal
government, the Tor service did not collaborate with the NSA to reveal
identities of users.<ref name="wp-feds-pay" />

Critics say that Tor is not as secure as it claims,<ref>{{Cite news
|date=2 September 2013 |title=Tor is Not as Safe as You May Think
|work=Infosecurity magazine
|url=http://www.infosecurity-magazine.com/news/tor-is-not-as-safe-as-you-may-think/
|access-date=30 August 2014 |archive-date=27 August 2014
|archive-url=https://web.archive.org/web/20140827203552/http://www.infosecurity-magazine.com/news/tor-is-not-as-safe-as-you-may-think/
|url-status=live }}</ref> pointing to U.S. law enforcement's
investigations and shutdowns of Tor-using sites such as web-hosting
company [[Freedom Hosting]] and online marketplace [[Silk Road
(marketplace)|Silk Road]].<ref name="pando" /> In October 2013, after
analyzing documents leaked by Edward Snowden, ''The Guardian''
reported that the NSA had repeatedly tried to crack Tor and had failed
to break its core security, although it had had some success attacking
the computers of individual Tor users.<ref name="guardian-nsa-target"
/> ''The Guardian'' also published a 2012 NSA classified slide deck,
entitled "Tor Stinks", which said: "We will never be able to
de-anonymize all Tor users all the time", but "with manual analysis we
can de-anonymize a very small fraction of Tor users".<ref>{{Cite news
|date=4 October 2014 |title='Tor Stinks' presentation – read the full
document |work=The Guardian
|url=https://www.theguardian.com/world/interactive/2013/oct/04/tor-stinks-nsa-presentation-document
|access-date=30 August 2014 |archive-date=29 August 2014
|archive-url=https://web.archive.org/web/20140829193451/http://www.theguardian.com/world/interactive/2013/oct/04/tor-stinks-nsa-presentation-document
|url-status=live }}</ref> When Tor users are arrested, it is typically
due to human error, not to the core technology being hacked or
cracked.<ref>{{cite web |last=O'Neill |first=Patrick Howell |date=2
October 2014 |title=The real chink in Tor's armor
|url=http://www.dailydot.com/crime/silk-road-tor-arrests/ |website=The
Daily Dot |access-date=3 October 2014 |archive-date=25 May 2019
|archive-url=https://web.archive.org/web/20190525124144/https://www.dailydot.com/crime/silk-road-tor-arrests/
|url-status=live }}</ref> On 7 November 2014, for example, a joint
operation by the FBI, ICE Homeland Security investigations and
European Law enforcement agencies led to 17 arrests and the seizure of
27 sites containing 400 pages.<ref name="arrests" />{{Dubious |
reason=The operation is so successful most likely because of Tor's
protocol weakness. Not a good example. (See "Relay early traffic
confirmation attack" above.) |date=July 2018}} A late 2014 report by
''[[Der Spiegel]]'' using a new cache of Snowden leaks revealed,
however, that {{as of|2012|lc=y}} the NSA deemed Tor on its own as a
"major threat" to its mission, and when used in conjunction with other
privacy tools such as [[Off-the-Record Messaging|OTR]], Cspace,
[[ZRTP]], [[RedPhone]], [[Tails (operating system)|Tails]], and
[[TrueCrypt]] was ranked as "catastrophic," leading to a "near-total
loss/lack of insight to target communications, presence..."<ref
name="spiegel1" /><ref name="spiegel2" />

=== 2011 ===
In March 2011, The Tor Project received the [[Free Software
Foundation]]'s 2010 Award for Projects of Social Benefit. The citation
read, "Using free software, Tor has enabled roughly 36 million people
around the world to experience freedom of access and expression on the
Internet while keeping them in control of their privacy and anonymity.
Its network has proved pivotal in dissident movements in both [[Iran]]
and more recently [[Egypt]]."<ref name="fsf-award" />

=== 2012 ===
In 2012, ''[[Foreign Policy]]'' magazine named Dingledine, Mathewson,
and Syverson among its Top 100 Global Thinkers "for making the web
safe for whistleblowers".<ref name="fp-top100-thinkers" />

=== 2013 ===
In 2013, [[Jacob Appelbaum]] described Tor as a "part of an ecosystem
of software that helps people regain and reclaim their autonomy. It
helps to enable people to have agency of all kinds; it helps others to
help each other and it helps you to help yourself. It runs, it is open
and it is supported by a large community spread across all walks of
life."<ref name="verge-applebaum" />

In June 2013, whistleblower [[Edward Snowden]] used Tor to send
information about [[PRISM (surveillance program)|PRISM]] to ''[[The
Washington Post]]'' and ''[[The Guardian]]''.<ref name="erste-darknet"
/>

=== 2014 ===
In 2014, the Russian government offered a $111,000 contract to "study
the possibility of obtaining technical information about users and
users' equipment on the Tor anonymous network".<ref name="ars-111k"
/><ref name="pcw-111k" />

In September 2014, in response to reports that [[Comcast]] had been
discouraging customers from using the Tor Browser, [[Comcast]] issued
a public statement that "We have no policy against Tor, or any other
browser or software."<ref>{{cite web
|url=https://corporate.comcast.com/comcast-voices/setting-the-record-straight-on-tor
|title=Setting the Record Straight on Tor |first=Jason |last=Livingood
|date=2014-09-15 |quote=The report may have generated a lot of clicks
but is totally inaccurate. Comcast is not asking customers to stop
using Tor, or any other browser for that matter. We have no policy
against Tor, or any other browser or software. Customers are free to
use their Xfinity Internet service to visit any website, use any app,
and so forth. ... Comcast doesn't monitor our customer's browser
software, web surfing or online history. |access-date=5 January 2021
|archive-date=4 January 2021
|archive-url=https://web.archive.org/web/20210104165011/https://corporate.comcast.com/comcast-voices/setting-the-record-straight-on-tor
|url-status=live }}</ref>

In October 2014, The Tor Project hired the public relations firm
Thomson Communications to improve its public image (particularly
regarding the terms "Dark Net" and "hidden services," which are widely
viewed as being problematic) and to educate journalists about the
technical aspects of Tor.<ref>{{cite web |last=O'Neill |first=Patrick
Howell |date=26 March 2015 |title=Tor's great rebranding
|url=http://www.dailydot.com/politics/tor-media-public-relations-perception/
|access-date=19 April 2015 |website=The Daily Dot |archive-date=12
April 2015 |archive-url=https://web.archive.org/web/20150412172355/http://www.dailydot.com/politics/tor-media-public-relations-perception/
|url-status=live }}</ref>

=== 2015 ===
In June 2015, the [[United Nations special rapporteur|special
rapporteur]] from the United Nations' [[Office of the High
Commissioner for Human Rights]] specifically mentioned Tor in the
context of the debate in the U.S. about allowing so-called [[backdoor
(computing)|backdoors]] in encryption programs for law enforcement
purposes<ref>{{Cite news |last=Peterson |first=Andrea |date=28 May
2015 |title=U.N. report: Encryption is important to human rights — and
backdoors undermine it
|url=https://www.washingtonpost.com/blogs/the-switch/wp/2015/05/28/un-report-encryption-is-important-to-human-rights-and-backdoors-undermine-it
|newspaper=The Washington Post |access-date=17 September 2017
|archive-date=23 June 2015
|archive-url=https://web.archive.org/web/20150623030700/http://www.washingtonpost.com/blogs/the-switch/wp/2015/05/28/un-report-encryption-is-important-to-human-rights-and-backdoors-undermine-it/
|url-status=live }}</ref> in an interview for ''The Washington Post''.

In July 2015, the Tor Project announced an alliance with the [[Library
Freedom Project]] to establish exit nodes in public
libraries.<ref>{{cite web |title=Tor Exit Nodes in Libraries – Pilot
(phase one) |url=https://blog.torproject.org/blog/tor-exit-nodes-libraries-pilot-phase-one
|access-date=15 September 2015 |website=Tor Project.org
|archive-date=8 September 2015
|archive-url=https://web.archive.org/web/20150908012811/https://blog.torproject.org/blog/tor-exit-nodes-libraries-pilot-phase-one
|url-status=live }}</ref><ref>{{cite web |title=Library Freedom
Project |url=https://libraryfreedomproject.org/ |access-date=15
September 2015 |website=libraryfreedomproject.org |archive-date=19
September 2015 |archive-url=https://web.archive.org/web/20150919100044/https://libraryfreedomproject.org/
|url-status=live }}</ref> The pilot program, which established a
middle relay running on the excess bandwidth afforded by the Kilton
Library in [[Lebanon, New Hampshire]], making it the first library in
the U.S. to host a Tor node, was briefly put on hold when the local
city manager and deputy sheriff voiced concerns over the cost of
defending search warrants for information passed through the Tor exit
node. Although the <abbr title="US. Department of Homeland
Security">DHS</abbr> had alerted New Hampshire authorities to the fact
that Tor is sometimes used by criminals, the Lebanon Deputy Police
Chief and the Deputy City Manager averred that no pressure to
strong-arm the library was applied, and the service was re-established
on 15 September 2015.<ref>{{cite web |last=Doyle-Burr |first=Nora
|date=16 September 2015 |title=Despite Law Enforcement Concerns,
Lebanon Board Will Reactivate Privacy Network Tor at Kilton Library
|url=http://www.vnews.com/photos/inthenews/18620952-95/despite-law-enforcement-concerns-lebanon-board-will-reactivate-privacy-network-tor-at-kilton-library
|url-status=dead
|archive-url=https://web.archive.org/web/20150918031540/http://www.vnews.com/photos/inthenews/18620952-95/despite-law-enforcement-concerns-lebanon-board-will-reactivate-privacy-network-tor-at-kilton-library
|archive-date=18 September 2015 |access-date=20 November 2015
|website=Valley News}}</ref> U.S. Rep. [[Zoe Lofgren]] (D-Calif)
released a letter on 10 December 2015, in which she asked the <abbr
title="US. Department of Homeland Security">DHS</abbr> to clarify its
procedures, stating that "While the Kilton Public Library's board
ultimately voted to restore their Tor relay, I am no less disturbed by
the possibility that <abbr title="US. Department of Homeland
Security">DHS</abbr> employees are pressuring or persuading public and
private entities to discontinue or degrade services that protect the
privacy and anonymity of U.S. citizens."<ref>{{cite web |date=10
December 2015 |title=Lofgren questions DHS policy towards Tor Relays
|url=https://lofgren.house.gov/news/documentsingle.aspx?DocumentID=398038
|url-status=dead
|archive-url=https://web.archive.org/web/20160603144959/https://lofgren.house.gov/news/documentsingle.aspx?DocumentID=398038
|archive-date=3 June 2016 |access-date=4 June 2016
|website=house.gov}}</ref><ref>{{cite web |last=Geller |first=Eric
|date=11 December 2015 |title=Democratic lawmaker wants to know if DHS
is sabotaging plans for Tor exit relays
|url=http://www.dailydot.com/politics/tor-libraries-dhs-zoe-lofgren-letter/
|access-date=4 June 2016 |website=The Daily Dot |archive-date=10 June
2016 |archive-url=https://web.archive.org/web/20160610194930/http://www.dailydot.com/politics/tor-libraries-dhs-zoe-lofgren-letter/
|url-status=live }}</ref><ref name="Kopstein2015">{{cite web
|last=Kopfstein |first=Janus |date=12 December 2015
|title=Congresswoman Asks Feds Why They Pressured a Library to Disable
Its Tor Node |url=https://motherboard.vice.com/read/congresswoman-asks-feds-why-they-pressured-a-library-to-disable-its-tor-node
|url-status=live
|archive-url=https://web.archive.org/web/20151222171028/http://motherboard.vice.com/read/congresswoman-asks-feds-why-they-pressured-a-library-to-disable-its-tor-node
|archive-date=22 December 2015 |website=Motherboard}}</ref> In a 2016
interview, Kilton Library IT Manager Chuck McAndrew stressed the
importance of getting libraries involved with Tor: "Librarians have
always cared deeply about protecting privacy, intellectual freedom,
and [[access to information]] (the freedom to read). Surveillance
has a very well-documented chilling effect on intellectual freedom. It
is the job of librarians to remove barriers to
information."<ref>{{Cite news |date=4 August 2016 |title=Tor crusader
discuss privacy, freedom with ExpressVPN |language=en-US |work=Home of
internet privacy
|url=https://www.expressvpn.com/blog/chuck-mcandrew-defends-tor/
|access-date=11 September 2017 }}</ref> The second library to host a
Tor node was the Las Naves Public Library in [[Valencia]], Spain,
implemented in the first months of 2016.<ref>{{Cite news |last=Gonzalo
|first=Marilín |date=26 January 2016 |title=Esta biblioteca valenciana
es la segunda del mundo en unirse al proyecto Tor |language=es
|work=El Diario
|url=http://www.eldiario.es/cultura/tecnologia/privacidad/biblioteca-Valencia-primera-Unidos-Tor_0_476303147.html
|access-date=4 March 2016 |archive-date=7 March 2016
|archive-url=https://web.archive.org/web/20160307091514/http://www.eldiario.es/cultura/tecnologia/privacidad/biblioteca-Valencia-primera-Unidos-Tor_0_476303147.html
|url-status=live }}</ref>

In August 2015, an [[IBM]] security research group, called "X-Force",
put out a quarterly report that advised companies to block Tor on
security grounds, citing a "steady increase" in attacks from Tor exit
nodes as well as botnet traffic.<ref>{{cite web |last=Broersma
|first=Matthew |date=26 August 2015 |title=IBM Tells Companies To
Block Tor Anonymisation Network
|url=http://www.techweekeurope.co.uk/security/ibm-companies-tor-175468
|access-date=15 September 2015 |website=TechWeekEurope UK
|archive-date=10 September 2015
|archive-url=https://web.archive.org/web/20150910211854/http://www.techweekeurope.co.uk/security/ibm-companies-tor-175468
|url-status=live }}</ref>

In September 2015, Luke Millanta created OnionView, a web service that
plots the location of active Tor relay nodes onto an interactive map
of the world. The project's purpose was to detail the network's size
and escalating growth rate.<ref>{{Cite magazine |last=Greenberg
|first=Andy |date=14 September 2015 |title=Mapping How Tor's Anonymity
Network Spread Around the World
|url=https://www.wired.com/2015/09/mapping-tors-anonymity-network-spread-around-world/
|magazine=Wired |access-date=9 February 2016 |archive-date=3 February
2016 |archive-url=https://web.archive.org/web/20160203154307/http://www.wired.com/2015/09/mapping-tors-anonymity-network-spread-around-world
|url-status=live }}</ref>

In December 2015, [[Daniel Ellsberg]] (of the [[Pentagon
Papers]]),<ref>{{cite web |date=26 December 2015 |title=This is What a
Tor Supporter Looks Like: Daniel Ellsberg
|url=https://blog.torproject.org/blog/what-tor-supporter-looks-daniel-ellsberg
|access-date=4 June 2016 |website=The Tor Blog |archive-date=4 March
2016 |archive-url=https://web.archive.org/web/20160304100212/https://blog.torproject.org/blog/what-tor-supporter-looks-daniel-ellsberg
|url-status=live }}</ref> [[Cory Doctorow]] (of [[Boing
Boing]]),<ref>{{cite web |date=18 December 2015 |title=This is What a
Tor Supporter Looks Like: Cory Doctorow
|url=https://blog.torproject.org/blog/what-tor-supporter-looks-cory-doctorow
|access-date=4 June 2016 |website=The Tor Blog |archive-date=16 June
2016 |archive-url=https://web.archive.org/web/20160616210816/https://blog.torproject.org/blog/what-tor-supporter-looks-cory-doctorow
|url-status=live }}</ref> [[Edward Snowden]],<ref>{{cite web |date=30
December 2015 |title=This is What a Tor Supporter Looks Like: Edward
Snowden |url=https://blog.torproject.org/blog/what-tor-supporter-looks-edward-snowden
|access-date=4 June 2016 |website=The Tor Blog |archive-date=9 April
2016 |archive-url=https://web.archive.org/web/20160409024736/https://blog.torproject.org/blog/what-tor-supporter-looks-edward-snowden
|url-status=live }}</ref> and artist-activist [[Molly
Crabapple]],<ref>{{cite web |date=9 December 2015 |title=This is what
a Tor Supporter looks like: Molly Crabapple
|url=https://blog.torproject.org/blog/what-tor-supporter-looks-molly-crabapple
|access-date=4 June 2016 |website=The Tor Blog |archive-date=16 June
2016 |archive-url=https://web.archive.org/web/20160616210748/https://blog.torproject.org/blog/what-tor-supporter-looks-molly-crabapple
|url-status=live }}</ref> amongst others, announced their support of
Tor.

=== 2016 ===
In March 2016, New Hampshire state representative [[Keith Ammon]]
introduced a bill<ref>{{cite web |date=10 March 2016 |title=House Bill
1508: An Act allowing public libraries to run certain privacy software
|url=http://www.gencourt.state.nh.us/bill_status/billText.aspx?id=796&txtFormat=html
|access-date=4 June 2016 |website=New Hampshire State Government
|archive-date=11 April 2017
|archive-url=https://web.archive.org/web/20170411043230/http://www.gencourt.state.nh.us/bill_status/billText.aspx?id=796&txtFormat=html
|url-status=live }}</ref> allowing public libraries to run privacy
software. The bill specifically referenced Tor. The text was crafted
with extensive input from [[Alison Macrina]], the director of the
[[Library Freedom Project]].<ref name="Proposed New Hampshire
bill">{{cite web |last=O'Neill |first=Patrick Howell |date=18 February
2016 |title=New Hampshire bill allows for libraries' usage of
encryption and privacy software
|url=http://www.dailydot.com/politics/new-hampshire-tor-library-legislation/
|access-date=10 March 2016 |website=The Daily Dot |archive-date=11
March 2016 |archive-url=https://web.archive.org/web/20160311073326/http://www.dailydot.com/politics/new-hampshire-tor-library-legislation/
|url-status=live }}</ref> The bill was passed by the House
268–62.<ref>{{cite web |title=New Hampshire HB1508 – 2016 – Regular
Session |url=https://legiscan.com/NH/text/HB1508/id/1288060
|access-date=4 June 2016 |website=legiscan.com |archive-date=29 July
2016 |archive-url=https://web.archive.org/web/20160729171429/https://legiscan.com/NH/text/HB1508/id/1288060
|url-status=live }}</ref>

Also in March 2016, the first Tor node, specifically a middle relay,
was established at a library in Canada, the Graduate Resource Centre
(GRC) in the Faculty of Information and Media Studies (FIMS) at the
[[University of Western Ontario]].<ref name="Western FIMS
relay">{{cite web |date=14 March 2016 |title=Library in FIMS joins
global network fighting back against digital surveillance, censorship,
and the obstruction of information
|url=http://www.fims.uwo.ca/news/2016/library_in_fims_joins_global_network_fighting_back_against_digital_surveillance_censorship_and_the_obstruction_of_information.html
|access-date=16 March 2016 |website=FIMS News |archive-date=20 March
2016 |archive-url=https://web.archive.org/web/20160320112332/http://www.fims.uwo.ca/news/2016/library_in_fims_joins_global_network_fighting_back_against_digital_surveillance_censorship_and_the_obstruction_of_information.html
|url-status=live }}</ref> Given that the running of a Tor exit node is
an unsettled area of Canadian law,<ref name="Legality of running a Tor
exit node in Canada">{{cite web |last=Pearson |first=Jordan |date=25
September 2015 |title=Can You Be Arrested for Running a Tor Exit Node
In Canada? |url=https://motherboard.vice.com/read/can-you-be-arrested-for-running-a-tor-exit-node-in-canada
|access-date=16 March 2016 |website=Motherboard |archive-date=23 March
2016 |archive-url=https://web.archive.org/web/20160323231601/https://motherboard.vice.com/read/can-you-be-arrested-for-running-a-tor-exit-node-in-canada
|url-status=live }}</ref> and that in general institutions are more
capable than individuals to cope with legal pressures, Alison Macrina
of the Library Freedom Project has opined that in some ways she would
like to see intelligence agencies and law enforcement attempt to
intervene in the event that an exit node were established.<ref
name="Fighting the Feds on running a Tor node">{{cite web
|last=Pearson |first=Jordan |date=16 March 2016 |title=Canadian
Librarians Must Be Ready to Fight the Feds on Running a Tor Node
|url=https://motherboard.vice.com/en_ca/read/canadian-librarians-must-be-ready-to-fight-the-feds-on-running-a-tor-node-western-library-freedom-project
|access-date=16 March 2016 |website=Motherboard |archive-date=19 March
2016 |archive-url=https://web.archive.org/web/20160319083936/http://motherboard.vice.com/en_ca/read/canadian-librarians-must-be-ready-to-fight-the-feds-on-running-a-tor-node-western-library-freedom-project
|url-status=live }}</ref>

On 16 May 2016, [[CNN]] reported on the case of core Tor developer
isis agora lovecruft,<ref name="lovecruft 2020 tweet">{{cite web
|url=https://twitter.com/isislovecruft/status/1258515495851921408
|last=lovecruft |first=isis agora |title=May 7, 2020 Tweet
|date=2020-05-07 |quote=my name is isis agora lovecruft not Isis Agora
Lovecruft}}</ref> who had fled to Germany under the threat of a
subpoena by the FBI during the Thanksgiving break of the previous
year. The [[Electronic Frontier Foundation]] legally represented
lovecruft.<ref name="Harassment of Isis Agora Lovecruft">{{cite web
|last=Pagliery |first=Jose |date=17 May 2016 |title=Developer of
anonymous Tor software dodges FBI, leaves US
|url=https://money.cnn.com/2016/05/17/technology/tor-developer-fbi/index.html
|access-date=17 May 2016 |website=CNN |archive-date=17 May 2016
|archive-url=https://web.archive.org/web/20160517153400/http://money.cnn.com/2016/05/17/technology/tor-developer-fbi/index.html
|url-status=live }}</ref>

On 2 December 2016, ''[[The New Yorker]]'' reported on burgeoning
[[digital privacy]] and security workshops in the [[San Francisco Bay
Area]], particularly at the [[hackerspace]] [[Noisebridge]], in the
wake of the [[2016 United States presidential election]]; downloading
the Tor browser was mentioned.<ref name="Trump Preparerdness">{{Cite
magazine |last=Weiner |first=Anna |date=2 December 2016 |title=Trump
Preparedness: Digital Security 101
|url=https://www.newyorker.com/culture/culture-desk/trump-preparedness-digital-security-101
|magazine=The New Yorker |access-date=20 February 2020
|archive-date=25 October 2020
|archive-url=https://web.archive.org/web/20201025144947/https://www.newyorker.com/culture/culture-desk/trump-preparedness-digital-security-101
|url-status=live }}</ref> Also, in December 2016, Turkey has blocked
the usage of Tor, together with ten of the most used [[VPN]] services
in Turkey, which were popular ways of accessing banned social media
sites and services.<ref>{{cite web |date=19 December 2016
|title=Turkey Partially Blocks Access to Tor and Some VPNs
|url=https://www.bleepingcomputer.com/news/government/turkey-partially-blocks-access-to-tor-and-some-vpns/}}</ref>

Tor (and [[Bitcoin]]) was fundamental to the operation of the darkweb
marketplace [[AlphaBay]], which was taken down in an international law
enforcement operation in July 2017.<ref name="forfeit">{{cite web
|date=20 July 2017 |title=Forfeiture Complaint
|url=https://www.justice.gov/opa/press-release/file/982821/download
|publisher=Justice.gov |page=27 |access-date=28 July 2017
|archive-date=23 September 2020
|archive-url=https://web.archive.org/web/20200923012828/https://www.justice.gov/opa/press-release/file/982821/download
|url-status=live }}</ref> Despite federal claims that Tor would not
shield a user, however,<ref name="Ten times the size of Silk
Road.">{{cite web |last=Leyden |first=John |date=20 July 2017
|title=Cops harpoon two dark net whales in megabust: AlphaBay and
Hansa : Tor won't shield you, warn Feds
|url=https://www.theregister.co.uk/2017/07/20/dark_net_megabust/
|access-date=21 July 2017 |website=The Register |archive-date=23 May
2020 |archive-url=https://web.archive.org/web/20200523085637/https://www.theregister.co.uk/2017/07/20/dark_net_megabust/
|url-status=live }}</ref> elementary [[operational security]] errors
outside of the ambit of the Tor network led to the site's
downfall.<ref name="Operational Security Nonexistant">{{cite web
|last=McCarthy |first=Kieren |date=20 July 2017 |title=Alphabay
shutdown: Bad boys, bad boys, what you gonna do? Not use your
Hotmail... ...or the Feds will get you ♪
|url=https://www.theregister.co.uk/2017/07/20/alphabay_hotmail_fbi/
|access-date=21 July 2017 |website=The Register |archive-date=23 May
2020 |archive-url=https://web.archive.org/web/20200523085638/https://www.theregister.co.uk/2017/07/20/alphabay_hotmail_fbi/
|url-status=live }}</ref>

=== 2017 ===
In June 2017 the [[Democratic Socialists of America]] recommended
intermittent Tor usage.<ref>{{cite web
|url=https://www.dsausa.org/organize/info_security/ |title=Information
Security Memo for Members |date=2017-07-11 |publisher=[[Democratic
Socialists of America]] |access-date=20 January 2021 |archive-date=20
January 2021 |archive-url=https://web.archive.org/web/20210120104155/https://www.dsausa.org/organize/info_security/
|url-status=live }}</ref><ref>{{cite web
|url=https://www.dsausa.org/files/2017/07/DSAInformationSecurityRecommendations_June2017.pdf
|title=INFORMATION SECURITY RECOMMENDATIONS |date=June 2017
|publisher=[[Democratic Socialists of America]] |access-date=20
January 2021 |archive-date=7 September 2020
|archive-url=https://web.archive.org/web/20200907193927/https://www.dsausa.org/files/2017/07/DSAInformationSecurityRecommendations_June2017.pdf
|url-status=live }}</ref> And in August 2017, according to reportage
cybersecurity firms which specialize in monitoring and researching the
dark Web (which relies on Tor as its infrastructure) on behalf of
banks and retailers routinely share their findings with the [[FBI]]
and with other law enforcement agencies "when possible and necessary"
regarding illegal content. The Russian-speaking underground offering a
crime-as-a-service model is regarded as being particularly robust.<ref
name="Dark Web Mainstream Media Coverage">{{cite web |last=Johnson
|first=Tim |date=2 August 2017 |title=Shocked by gruesome crime, cyber
execs help FBI on dark web
|url=http://www.idahostatesman.com/news/nation-world/national/article164797842.html
|website=Idaho Statesman}}</ref>

=== 2018 ===
In June 2018, Venezuela blocked access to the Tor network. The block
affected both direct connections to the network and connections being
made via bridge relays.<ref name="Venezuela Blocks Tor">{{cite web
|last=Brandom |first=Russell |date=25 June 2018 |title=Venezuela is
blocking access to the Tor network 16 Just days after new web blocks
were placed on local media outlets
|url=https://www.theverge.com/2018/6/25/17503680/venezuela-tor-blocked-web-censorship
|access-date=26 June 2018 |website=The Verge |archive-date=26 June
2018 |archive-url=https://web.archive.org/web/20180626000651/https://www.theverge.com/2018/6/25/17503680/venezuela-tor-blocked-web-censorship
|url-status=live }}</ref>

On 20 June 2018, Bavarian police raided the homes of the board members
of the non-profit Zwiebelfreunde, a member of [[torservers.net]],
which handles the European financial transactions of [[riseup]].net in
connection with a blog post there which apparently promised violence
against the upcoming [[Alternative for Germany]] convention.<ref
name="June 2018 Bavarian Raid">{{cite web |last=Grauer |first=Yael
|date=4 July 2018 |title=German police raid homes of Tor-linked
group's board members One board member described the police's
justification for the raids as a "tenuous" link between the privacy
group, a blog, and its email address
|url=https://www.zdnet.com/article/german-police-raid-homes-of-tor-linked-groups-board-members/
|access-date=6 July 2018 |website=ZDNet |archive-date=6 July 2018
|archive-url=https://web.archive.org/web/20180706000125/https://www.zdnet.com/article/german-police-raid-homes-of-tor-linked-groups-board-members/
|url-status=live }}</ref><ref name="Police searches homes of
Zwiebelfreunde board members as well as OpenLab in Augsburg">{{cite
web |last=n/a |first=46halbe |date=4 July 2018 |title=Police searches
homes of "Zwiebelfreunde" board members as well as "OpenLab" in
Augsburg |url=https://www.ccc.de/en/updates/2018/hausdurchsuchungen-bei-vereinsvorstanden-der-zwiebelfreunde-und-im-openlab-augsburg
|access-date=6 July 2018 |website=Chaos Computer Club |archive-date=4
July 2018 |archive-url=https://web.archive.org/web/20180704101613/https://www.ccc.de/en/updates/2018/hausdurchsuchungen-bei-vereinsvorstanden-der-zwiebelfreunde-und-im-openlab-augsburg
|url-status=live }}</ref> Tor came out strongly against the raid
against its support organization, which provides legal and financial
aid for the setting up and maintenance of high-speed relays and exit
nodes.<ref name="In Support of Torservers">{{cite web |last=Stelle
|first=Sharon |date=5 July 2018 |title=In Support of Torservers
|url=https://blog.torproject.org/support-torservers |access-date=6
July 2018 |website=TorProject.org |archive-date=7 July 2018
|archive-url=https://web.archive.org/web/20180707042439/https://blog.torproject.org/support-torservers
|url-status=live }}</ref> According to Torservers.net, on 23 August
2018 the German court at Landgericht München ruled that the raid and
seizures were illegal. The hardware and documentation seized had been
kept under seal, and purportedly were neither analyzed nor evaluated
by the Bavarian police.<ref>{{cite web |date=24 August 2018
|title=Gericht urteilt: Durchsuchung bei Zwiebelfreunden war
rechtswidrig [Update]
|url=https://netzpolitik.org/2018/gericht-urteilt-durchsuchung-bei-zwiebelfreunden-war-rechtswidrig/
|access-date=1 December 2019 |archive-date=12 October 2019
|archive-url=https://web.archive.org/web/20191012011235/https://netzpolitik.org/2018/gericht-urteilt-durchsuchung-bei-zwiebelfreunden-war-rechtswidrig/
|url-status=live }}</ref><ref>{{cite web |title=LG München I:
Hausdurchsuchungen bei Verein Zwiebelfreunde waren rechtswidrig
|url=https://rsw.beck.de/aktuell/meldung/lg-muenchen-i-hausdurchsuchungen-bei-netzaktivisten-rechtswidrig
|website=Aktuell |access-date=1 December 2019 |archive-date=15
February 2021 |archive-url=https://web.archive.org/web/20210215083404/https://rsw.beck.de/aktuell/daily/meldung/detail/lg-muenchen-i-hausdurchsuchungen-bei-netzaktivisten-rechtswidrig
|url-status=live }}</ref>

Since October 2018, [[internet in China|Chinese online communities]]
within Tor have begun to dwindle due to increased efforts to stop them
by the Chinese government.<ref>{{cite web |year=2018 |title=China's
clampdown on Tor pushes its hackers into foreign backyards
|website=[[The Register]]
|url=https://www.theregister.co.uk/2018/10/10/russia_china_hacker_forum_comparison
|access-date=10 October 2018 |archive-date=10 October 2018
|archive-url=https://web.archive.org/web/20181010184728/https://www.theregister.co.uk/2018/10/10/russia_china_hacker_forum_comparison/
|url-status=live }}</ref>

=== 2019 ===
In November 2019, [[Edward Snowden]] called for a full, unabridged
[[simplified Chinese]] translation of his autobiography, ''[[Permanent
Record (autobiography)|Permanent Record]]'', as the Chinese publisher
had violated their agreement by expurgating all mentions of Tor and
other matters deemed politically sensitive by the [[Chinese Communist
Party]].<ref name="Edward Snowden blew the whistle on how Chinese
censors scrubbed his book">{{cite web |last=Stegner |first=Isabella
|date=12 November 2019 |title=Edward Snowden blew the whistle on how
Chinese censors scrubbed his book
|url=https://qz.com/1746780/edward-snowden-calls-out-chinese-censorship-of-his-book/
|url-status=live
|archive-url=https://web.archive.org/web/20191115103544/https://qz.com/1746780/edward-snowden-calls-out-chinese-censorship-of-his-book/
|archive-date=15 November 2019 |access-date=12 November 2019
|website=Quartz}}</ref><ref>{{cite web |last=Snowden |first=Edward
|date=11 November 2019 |title=The Chinese edition of my new book,
#PermanentRecord, has just been censored.
|url=https://twitter.com/Snowden/status/1194092273170038784
|url-status=live
|archive-url=https://web.archive.org/web/20191112032031/https://twitter.com/Snowden/status/1194092273170038784
|archive-date=12 November 2019 |access-date=8 December 2019
|website=Twitter (@Snowden) |language=en }}</ref>

=== 2021 ===
On 8 December 2021, the Russian government agency [[Federal Service
for Supervision of Communications, Information Technology and Mass
Media|Roskomnadzor]] announced it has banned Tor and six VPN services
for failing to abide by the [[Russian Internet blacklist]].<ref>{{cite
web|date=2021-12-08|title=Russia Bans More VPN Products and TOR -
December 8, 2021|url=https://dailynewsbrief.com/2021/12/08/russia-bans-more-vpn-products-and-tor/|access-date=2021-12-11|website=Daily
NewsBrief|language=en-US}}</ref> Russian ISPs unsuccessfully attempted
to block Tor's main website as well as several bridges beginning on 1
December 2021.<ref>{{cite web |title=Russia Ratchets up Internet
Control by Blocking Privacy Service Tor
|url=https://www.usnews.com/news/technology/articles/2021-12-08/russia-ratchets-up-internet-crackdown-with-block-of-privacy-service-tor
|website=U.S. News & World Report |access-date=8 December 2021
|language=en}}</ref> The Tor Project has appealed to Russian courts
over this ban.<ref>{{cite web |title=Tor Project appeals Russian
court's decision to block access to Tor
|url=https://www.bleepingcomputer.com/news/security/tor-project-appeals-russian-courts-decision-to-block-access-to-tor/
|access-date=2022-03-08 |website=BleepingComputer
|language=en-us}}</ref>

=== 2022 ===
In response to [[Internet censorship]] in the [[Russo-Ukraine War]]
the [[BBC]] and [[VOA]] have directed Russian audiences to
Tor.<ref>{{cite web
|url=https://www.wsj.com/articles/russia-rolls-down-internet-iron-curtain-but-gaps-remain-11647087321
|title=Russia Rolls Down Internet Iron Curtain, but Gaps Remain
|work=The Wall Street Journal |last1=Schechner |first1=Sam
|last2=Hagey |first2=Keach |date=12 March 2022 |access-date=17 March
2022}}</ref> The Russian government increased efforts to block access
to Tor through technical and political means, and the network reported
an increase in traffic from Russia using its anti-censorship
[[Snowflake (software)|Snowflake tool]].<ref name=wired>{{cite
magazine|url=https://www.wired.com/story/tor-browser-russia-blocks/
|title=How Tor Is Fighting—and Beating—Russian Censorship |first=Matt
|last=Burgess |magazine=[[Wired (magazine)|WIRED]] |date=July 28, 2022
|access-date=2022-07-30}}</ref>

Iran implemented rolling internet blackouts during the [[Mahsa Amini
protests]], and Tor and Snowflake were used to circumvent them.<ref
name=skyrocket>{{cite news |last1=Browne |first1=Ryan |title=VPN use
skyrockets in Iran as citizens navigate internet censorship under
Tehran's crackdown
|url=https://www.cnbc.com/2022/10/07/vpn-use-skyrockets-in-iran-as-citizens-navigate-internet-censorship.html
|work=CNBC |language=en}}</ref><ref name=FAZ>{{cite news
|last1=Küchemann |first1=Fridtjof |title=Per Snowflake ins
TOR-Netzwerk: Online-Gasse für Menschen in Iran
|url=https://www.faz.net/aktuell/feuilleton/medien/zugang-fuer-iraner-per-snowflake-ins-tor-netzwerk-18346679.html
|work=[[Frankfurter Allgemeine Zeitung]] |date=27.09.2022
|language=de}}</ref><ref name=rnd>{{cite news |last1=Schwarzer
|first1=Matthias |title=Netzsperre im Iran umgehen: Wie "Snowflake"
einen Weg ins freie Internet ermöglicht - so kann der Westen helfen
|url=https://www.rnd.de/digital/netzsperre-im-iran-umgehen-wie-snowflake-einen-weg-ins-freie-internet-ermoeglicht-so-kann-der-westen-SE3LNI5BKNHJHGJJK2UZHWHXRA.html
|access-date=10 October 2022 |work=[[Redaktions Netzwerk Deutschland]]
|publisher=www.rnd.de |date=30.09.2022, 09:00 Uhr
|language=de}}</ref><ref name=EFF>{{cite web |last1=Quintin
|first1=Cooper |title=Snowflake Makes It Easy For Anyone to Fight
Censorship |url=https://www.eff.org/deeplinks/2022/10/snowflake-makes-it-easy-anyone-fight-censorship
|website=Electronic Frontier Foundation |language=en |date=4 October
2022}}</ref>

China, with its highly centralized control of its internet, had
effectively blocked Tor.<ref name=wired/>

== Improved security ==
Tor responded to earlier vulnerabilities listed above by patching them
and improving security. In one way or another, human (user) errors can
lead to detection. The Tor Project website provides the best practices
(instructions) on how to properly use the Tor browser. When improperly
used, Tor is not secure. For example, Tor warns its users that not all
traffic is protected; only the traffic routed through the Tor browser
is protected. Users are also warned to use [[HTTPS]] versions of
websites, not to [[BitTorrent|torrent]] with Tor, not to enable
browser plugins, not to open documents downloaded through Tor while
online, and to use safe bridges.<ref>{{cite web |title=The Tor Project
| Privacy & Freedom Online |url=https://torproject.org/
|website=torproject.org |access-date=31 October 2019 |archive-date=31
October 2019 |archive-url=https://web.archive.org/web/20191031195458/https://www.torproject.org/
|url-status=live }}</ref> Users are also warned that they cannot
provide their name or other revealing information in web forums over
Tor and stay anonymous at the same time.<ref name="stayan">{{cite web
|title=Tor: Overview – Staying anonymous
|url=https://www.torproject.org/about/overview.html.en |access-date=21
September 2016 |archive-date=6 June 2015
|archive-url=https://web.archive.org/web/20150606002957/https://www.torproject.org/about/overview.html.en
|url-status=live }}</ref>

Despite intelligence agencies' claims that 80% of Tor users would be
de-anonymized within 6 months in the year 2013,<ref
name="arstechnica.com">{{cite web |date=31 August 2016 |title=Building
a new Tor that can resist next-generation state surveillance
|url=https://arstechnica.com/security/2016/08/building-a-new-tor-that-withstands-next-generation-state-surveillance/
|access-date=13 September 2016 |website=arstechnica.com
|archive-date=11 September 2016
|archive-url=https://web.archive.org/web/20160911030754/http://arstechnica.com/security/2016/08/building-a-new-tor-that-withstands-next-generation-state-surveillance/
|url-status=live }}</ref> that has still not happened. In fact, as
late as September 2016, the FBI could not locate, de-anonymize and
identify the Tor user who hacked into the email account of a staffer
on [[Hillary Clinton]]'s email server.<ref>{{cite web |last=Francis
|first=Elias Groll, David |title=FBI: An Account on Clinton's Private
Email Server Was Hacked
|url=https://foreignpolicy.com/2016/09/02/fbi-an-account-on-clintons-private-email-server-was-hacked/
|access-date=2020-10-28 |website=Foreign Policy |language=en-US
|archive-date=31 October 2020
|archive-url=https://web.archive.org/web/20201031022316/https://foreignpolicy.com/2016/09/02/fbi-an-account-on-clintons-private-email-server-was-hacked/
|url-status=live }}</ref>

The best tactic of law enforcement agencies to de-anonymize users
appears to remain with Tor-relay adversaries running poisoned nodes,
as well as counting on the users themselves using the Tor browser
improperly. For example, downloading a video through the Tor browser
and then opening the same file on an unprotected hard drive while
online can make the users' real IP addresses available to
authorities.<ref>{{cite web |date=16 August 2016 |title=Aussie cops
ran child porn site for months, revealed 30 US IPs
|url=https://arstechnica.com/tech-policy/2016/08/aussie-cops-ran-child-porn-site-for-months-revealed-30-us-ips/
|access-date=13 September 2016 |website=arstechnica.com
|archive-date=8 September 2016
|archive-url=https://web.archive.org/web/20160908002444/http://arstechnica.com/tech-policy/2016/08/aussie-cops-ran-child-porn-site-for-months-revealed-30-us-ips/
|url-status=live }}</ref>

=== Odds of detection ===
When properly used, odds of being de-anonymized through Tor are said
to be extremely low. Tor project's co-founder [[Nick Mathewson]]
explained that the problem of "Tor-relay adversaries" running poisoned
nodes means that a theoretical adversary of this kind is not the
network's greatest threat:

{{quotation|"No adversary is truly global, but no adversary needs to
be truly global," he says. "Eavesdropping on the entire Internet is a
several-billion-dollar problem. Running a few computers to eavesdrop
on a lot of traffic, a selective denial of service attack to drive
traffic to your computers, that's like a tens-of-thousands-of-dollars
problem." At the most basic level, an attacker who runs two poisoned
Tor nodes—one entry, one exit—is able to analyse traffic and thereby
identify the tiny, unlucky percentage of users whose circuit happened
to cross both of those nodes. In 2016 the Tor network offers a total
of around 7,000 relays, around 2,000 guard (entry) nodes and around
1,000 exit nodes. So the odds of such an event happening are one in
two million ({{Frac|1|2000}} × {{Frac|1|1000}}), give or take."<ref
name="arstechnica.com" />}}

Tor does not provide protection against [[Timing attack|end-to-end
timing attack]]s: if an attacker can watch the traffic coming out of
the target computer, and also the traffic arriving at the target's
chosen destination (e.g. a server hosting a .onion site), that
attacker can use statistical analysis to discover that they are part
of the same circuit.<ref name=stayan/>

=== Levels of security ===
{{More citations needed section|date=December 2021}}

Depending on individual user needs, Tor browser offers three levels of
security located under the Security Level (the small gray shield at
the top-right of the screen) icon > Advanced Security Settings. In
addition to encrypting the data, including constantly changing an IP
address through a virtual circuit comprising successive, randomly
selected Tor relays, several other layers of security are at a user's
disposal:

# '''Standard (default) – at this security level, all browser features
are enabled.'''
#* This level provides the most usable experience, and the lowest
level of security.
# '''Safer – at this security level, the following changes apply:'''
#* JavaScript is disabled on non-HTTPS sites.
#* On sites where JavaScript is enabled, performance optimizations are
disabled. Scripts on some sites may run slower.
#* Some mechanisms of displaying math equations are disabled.
#* Audio and video (HTML5 media), and WebGL are click-to-play.
# '''Safest – at this security level, these additional changes apply:'''
#* JavaScript is disabled by default on all sites.
#* Some fonts, icons, math symbols, and images are disabled.
#* Audio and video (HTML5 media), and WebGL are click-to-play.

==See also==
<!-- Please keep entries in alphabetical order & add a short
description [[WP:SEEALSO]] -->
{{Div col|colwidth=20em|small=yes}}
* [[.onion]]
* [[Anonymous P2P]]
* [[Anonymous web browsing]]
* [[Briar (software)|Briar: messaging app on Tor network]]
* [[Crypto-anarchism]]
* [[Darknet]]
* [[Dark web]]
* [[Deep web]]
* [[Freedom of information]]
* [[Freenet]]
* [[GNUnet]]
* [[I2P]]
* [[Internet censorship]]
* [[Internet censorship circumvention]]
* [[Internet privacy]]
* [[Privoxy]]
* [[Proxy server]]
* [[Psiphon]]
* [[Tor2web]]
* [[Tor Phone]]
* [[torservers.net]]
{{div col end}}
<!-- Please keep entries in alphabetical order -->
{{Portal bar| Anarchism |Free and open-source software |Freedom of
speech |Internet }}

== Citations ==
{{Reflist|refs=

<ref name="spiegel2">{{Cite news |date=28 December 2014
|title=Presentation from the SIGDEV Conference 2012 explaining which
encryption protocols and techniques can be attacked and which not
|work=Der Spiegel |url=http://www.spiegel.de/media/media-35535.pdf
|access-date=23 January 2015 |archive-date=8 October 2018
|archive-url=https://web.archive.org/web/20181008114248/http://www.spiegel.de/media/media-35535.pdf
|url-status=live }}</ref>

<ref name="spiegel1">{{Cite news |last=SPIEGEL Staff |date=28 December
2014 |title=Prying Eyes: Inside the NSA's War on Internet Security
|work=Der Spiegel
|url=http://www.spiegel.de/international/germany/inside-the-nsa-s-war-on-internet-security-a-1010361.html
|access-date=23 January 2015 |archive-date=24 January 2015
|archive-url=https://web.archive.org/web/20150124202809/http://www.spiegel.de/international/germany/inside-the-nsa-s-war-on-internet-security-a-1010361.html
|url-status=live }}</ref>

<ref name="01-chercheurs">{{cite web |title=Des chercheurs Francais
cassent le reseau d'anonymisation Tor
|url=http://pro.01net.com/editorial/544024/des-chercheurs-francais-cassent-le-reseau-danonymisation-tor/
|access-date=17 October 2011 |website=01net.com |language=fr
|archive-date=16 October 2011
|archive-url=https://web.archive.org/web/20111016155325/http://pro.01net.com/editorial/544024/des-chercheurs-francais-cassent-le-reseau-danonymisation-tor/
|url-status=live }}</ref>

<ref name="andssy-sniper">{{Cite conference |last1=Jansen |first1=Rob
|last2=Tschorsch |first2=Florian |last3=Johnson |first3=Aaron
|last4=Scheuermann |first4=Björn |year=2014 |title=The Sniper Attack:
Anonymously Deanonymizing and Disabling the Tor Network
|url=http://www.robgjansen.com/publications/sniper-ndss2014.pdf
|conference=21st Annual Network & Distributed System Security
Symposium |access-date=28 April 2014 |archive-date=30 June 2014
|archive-url=https://web.archive.org/web/20140630044050/http://www.robgjansen.com/publications/sniper-ndss2014.pdf
|url-status=live }}</ref>

<ref name="ars-111k">{{cite web |last=Gallagher |first=Sean |date=25
July 2014 |title=Russia publicly joins war on Tor privacy with
$111,000 bounty
|url=https://arstechnica.com/security/2014/07/russia-publicly-joins-war-on-tor-privacy-with-111000-bounty/
|access-date=26 July 2014 |website=[[Ars Technica]] |archive-date=26
July 2014 |archive-url=https://web.archive.org/web/20140726214634/http://arstechnica.com/security/2014/07/russia-publicly-joins-war-on-tor-privacy-with-111000-bounty/
|url-status=live }}</ref>

<ref name="ars-feds-narcotics">{{cite web |last=Goodin |first=Dan
|date=16 April 2012 |title=Feds shutter online narcotics store that
used Tor to hide its tracks
|url=https://arstechnica.com/tech-policy/news/2012/04/feds-shutter-online-narcotics-store-that-used-tor-to-hide-its-tracks.ars?src=fbk
|access-date=20 April 2012 |website=[[Ars Technica]] |archive-date=19
April 2012 |archive-url=https://web.archive.org/web/20120419165308/http://arstechnica.com/tech-policy/news/2012/04/feds-shutter-online-narcotics-store-that-used-tor-to-hide-its-tracks.ars?src=fbk
|url-status=live }}</ref>

<ref name="ars-ranks-cut">{{cite web |last=Gallagher |first=Sean
|date=18 April 2014 |title=Tor network's ranks of relay servers cut
because of Heartbleed bug
|url=https://arstechnica.com/security/2014/04/tor-networks-ranks-of-relay-servers-cut-because-of-heartbleed-bug/
|access-date=28 April 2014 |website=[[Ars Technica]] |archive-date=1
May 2014 |archive-url=https://web.archive.org/web/20140501163047/http://arstechnica.com/security/2014/04/tor-networks-ranks-of-relay-servers-cut-because-of-heartbleed-bug/
|url-status=live }}</ref>

<ref name="bitmessage-faq">{{cite web |title=Bitmessage FAQ
|url=https://bitmessage.org/wiki/FAQ |access-date=17 July 2013
|website=Bitmessage |archive-date=18 August 2013
|archive-url=https://web.archive.org/web/20130818092419/https://bitmessage.org/wiki/FAQ
|url-status=live }}</ref>

<ref name="bbr-cleaning-up">{{cite web |last=Bode |first=Karl |date=12
March 2007 |title=Cleaning up Tor
|url=http://www.broadbandreports.com/shownews/Cleaning-Up-Tor-82218
|access-date=28 April 2014 |website=Broadband.com |archive-date=21
October 2013 |archive-url=https://web.archive.org/web/20131021185626/http://www.broadbandreports.com/shownews/Cleaning-Up-Tor-82218
|url-status=live }}</ref>

<ref name="bw-tor-vs">{{Cite news |last=Lawrence |first=Dune |date=23
January 2014 |title=The Inside Story of Tor, the Best Internet
Anonymity Tool the Government Ever Built |work=[[Bloomberg
Businessweek]] |url=http://www.businessweek.com/articles/2014-01-23/tor-anonymity-software-vs-dot-the-national-security-agency
|access-date=28 April 2014 |archive-date=29 March 2014
|archive-url=https://web.archive.org/web/20140329174719/http://www.businessweek.com/articles/2014-01-23/tor-anonymity-software-vs-dot-the-national-security-agency
|url-status=live }}</ref>

<ref name="boston-domestic-abuse">{{cite web |last=LeVines
|first=George |date=7 May 2014 |title=As domestic abuse goes digital,
shelters turn to counter-surveillance with Tor
|url=http://betaboston.com/news/2014/05/07/as-domestic-abuse-goes-digital-shelters-turn-to-counter-surveillance-with-tor/
|access-date=8 May 2014 |website=[[Boston Globe]] |archive-date=14
September 2014 |archive-url=https://web.archive.org/web/20140914153110/http://betaboston.com/news/2014/05/07/as-domestic-abuse-goes-digital-shelters-turn-to-counter-surveillance-with-tor/
|url-status=live }}</ref>

<ref name="boston-free-speech-tech">{{cite web |last=McKim
|first=Jenifer B. |date=8 March 2012 |title=Privacy software, criminal
use |url=http://articles.boston.com/2012-03-08/business/31136655_1_law-enforcement-free-speech-technology/2
|archive-url=https://web.archive.org/web/20120312225054/http://articles.boston.com/2012-03-08/business/31136655_1_law-enforcement-free-speech-technology/2
|archive-date=12 March 2012 |website=[[The Boston Globe]]}}</ref>

<ref name="ccsw-attacking">{{Cite conference |last1=Herrmann
|first1=Dominik |last2=Wendolsky |first2=Rolf |last3=Federrath
|first3=Hannes |date=13 November 2009 |title=Website Fingerprinting:
Attacking Popular {{sic|hide=y|Privacy Enhancing}} Technologies with
the Multinomial Naïve-Bayes Classifier
|url=http://epub.uni-regensburg.de/11919/1/authorsversion-ccsw09.pdf
|conference=Cloud Computing Security Workshop |location=New York, USA
|publisher=[[Association for Computing Machinery]] |access-date=2
September 2010 |book-title=Proceedings of the 2009 ACM Cloud Computing
Security Workshop (CCSW) |archive-date=22 April 2011
|archive-url=https://web.archive.org/web/20110422121714/http://epub.uni-regensburg.de/11919/1/authorsversion-ccsw09.pdf
|url-status=live }}</ref>

<ref name="cnet-arrested">{{Cite news |last=Soghoian |first=Chris
|date=16 September 2007 |title=Tor anonymity server admin arrested
|work=[[CNET Networks|CNET News]]
|url=http://news.cnet.com/8301-13739_3-9779225-46.html |access-date=17
January 2011 |archive-date=10 December 2010
|archive-url=https://web.archive.org/web/20101210151708/http://news.cnet.com/8301-13739_3-9779225-46.html
|url-status=live }}</ref>

<ref name="compaint-ulbricht">{{cite web |last=Turner |first=Serrin
|date=27 September 2013 |title=Sealed compaint
|url=http://www1.icsi.berkeley.edu/~nweaver/UlbrichtCriminalComplaint.pdf
|archive-url=https://web.archive.org/web/20131002221530/http://www1.icsi.berkeley.edu/~nweaver/UlbrichtCriminalComplaint.pdf
|archive-date=2 October 2013 |website=United States of America v. Ross
William Ulbricht}}</ref>

<ref name="cso-black-market">{{cite web |last=Gregg |first=Brandon
|date=30 April 2012 |title=How online black markets work
|url=http://www.csoonline.com/article/705316/how-online-black-markets-work
|access-date=6 August 2012 |website=CSO Online |archive-date=13 August
2012 |archive-url=https://web.archive.org/web/20120813131253/http://www.csoonline.com/article/705316/how-online-black-markets-work
|url-status=live }}</ref>

<ref name="economist-bitcoin">{{Cite news |date=29 September 2012
|title=Bitcoin: Monetarists Anonymous |newspaper=[[The Economist]]
|url=http://www.economist.com/node/21563752 |access-date=19 May 2013
|archive-date=20 October 2013
|archive-url=https://web.archive.org/web/20131020192331/http://www.economist.com/node/21563752
|url-status=live }}</ref>

<ref name="eff-silk-road">{{cite web |last=Higgins |first=Parker
|date=3 October 2013 |title=In the Silk Road Case, Don't Blame the
Technology |url=https://www.eff.org/deeplinks/2013/10/silk-road-case-dont-blame-technology
|access-date=22 December 2013 |website=[[Electronic Frontier
Foundation]] |archive-date=26 January 2014
|archive-url=https://web.archive.org/web/20140126154932/https://www.eff.org/deeplinks/2013/10/silk-road-case-dont-blame-technology
|url-status=live }}</ref>

<ref name="eff-ssd-tor">{{cite web |title=Surveillance Self-Defense:
Tor |url=https://ssd.eff.org/tech/tor |access-date=28 April 2014
|website=[[Electronic Frontier Foundation]] |archive-date=26 June 2014
|archive-url=https://web.archive.org/web/20140626031133/https://ssd.eff.org/tech/tor
|url-status=live }}</ref>

<ref name="erste-darknet">{{Cite news |last=Gaertner |first=Joachim
|date=1 July 2013 |title=Darknet – Netz ohne Kontrolle |language=de
|work=[[Das Erste]]
|url=http://www.daserste.de/information/wissen-kultur/ttt/sendung/br/20130630-ttt-darknet-102.html
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|archive-date=4 July 2013}}</ref>

<ref name="fsf-award">{{cite web |title=2010 Free Software Awards
announced |url=http://www.fsf.org/news/2010-free-software-awards-announced
|access-date=23 March 2011 |website=[[Free Software Foundation]]
|archive-date=1 May 2015
|archive-url=https://web.archive.org/web/20150501135149/http://www.fsf.org/news/2010-free-software-awards-announced
|url-status=live }}</ref>

<ref name="fp-top100-thinkers">{{cite web |last=Wittmeyer
|first=Alicia P.Q. |date=26 November 2012 |title=The FP Top 100 Global
Thinkers |url=https://foreignpolicy.com/articles/2012/11/26/the_fp_100_global_thinkers?page=0,48
|url-status=dead
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|website=[[Foreign Policy]]}}</ref>

<ref name="gawker-any-drug">{{cite web |last=Chen |first=Adrian
|date=1 June 2011 |title=The Underground Website Where You Can Buy Any
Drug Imaginable
|url=http://gawker.com/5805928/the-underground-website-where-you-can-buy-any-drug-imaginable
|url-status=dead
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|archive-date=3 June 2011 |access-date=20 April 2012
|website=Gawker}}</ref>

<ref name="gawker-kiddie-porn">{{cite web |last=Chen |first=Adrian
|date=11 June 2012 |title='Dark Net' Kiddie Porn Website Stymies FBI
Investigation |url=http://gawker.com/5916994/dark-net-kiddie-porn-website-stymies-fbi-investigation
|access-date=6 August 2012 |website=Gawker |archive-date=14 August
2012 |archive-url=https://web.archive.org/web/20120814195308/http://gawker.com/5916994/dark-net-kiddie-porn-website-stymies-fbi-investigation
|url-status=live }}</ref>

<ref name="ghowen-fby-analysis">{{cite web |last=Owen |first=Gareth
|title=FBI Malware Analysis
|url=http://ghowen.me/fbi-tor-malware-analysis |url-status=dead
|archive-url=https://web.archive.org/web/20140417081750/http://ghowen.me/fbi-tor-malware-analysis/
|archive-date=17 April 2014 |access-date=6 May
2014}}</ref>{{self-published inline |date=April 2014}}

<ref name="guardian-how-nsa">{{Cite news |last=Schneier |first=Bruce
|date=4 October 2013 |title=Attacking Tor: how the NSA targets users'
online anonymity |work=[[The Guardian]]
|url=https://www.theguardian.com/world/2013/oct/04/tor-attacks-nsa-users-online-anonymity
|access-date=22 December 2013 |archive-date=7 August 2017
|archive-url=https://web.archive.org/web/20170807074531/https://www.theguardian.com/world/2013/oct/04/tor-attacks-nsa-users-online-anonymity
|url-status=live }}</ref>

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<ref name="lj-portable">{{cite web |last=Knight |first=John |date=1
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<ref name="mirror-marques">{{Cite news |last=Best |first=Jessica
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<ref name="ml-rejecting">{{Cite mailing list
|url=https://lists.torproject.org/pipermail/tor-relays/2014-April/004336.html
|title=Rejecting 380 vulnerable guard/exit keys |date=16 April 2014b
|mailing-list=tor-relays |last=Dingledine |first=Roger |access-date=28
April 2014 |archive-date=19 April 2014
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<ref name="muckrock-hunting-porn">{{cite web |last=Morisy
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stymied by Tor undernet
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|access-date=6 August 2012 |website=Muckrock
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<ref name="openhub-tor">{{cite web |url=https://www.openhub.net/p/tor
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|book-title=Proceedings of the 2006 IEEE Symposium on Security and
Privacy |page=1 |publisher=IEEE CS Press |date=21 June 2006
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<ref name=prealpha>{{cite mailing list
|url=http://archives.seul.org/or/dev/Sep-2002/msg00019.html
|title=Pre-alpha: run an onion proxy now! |last=Dingledine
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<ref name="thn-compromised">{{cite web
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<ref name="torproject-fail-both-ends">{{cite web
|url=https://wiki.torproject.org/noreply/TheOnionRouter/TorFAQ?action=recall&rev=554#EntryGuards
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(like all current practical low-latency anonymity designs) fails when
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<ref name="torproject-faq-abuse">{{cite web
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<ref name="torproject-old-vulnerable">{{cite web
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<ref name="torproject-one-cell">{{cite web
|url=https://blog.torproject.org/blog/one-cell-enough |title=One cell
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<ref name="torproject-openssl-cve">{{cite web
|url=https://blog.torproject.org/blog/openssl-bug-cve-2014-0160
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<!-- ref name="torproject-pp">{{cite web
|url=https://trac.torproject.org/projects/tor/wiki/TheOnionRouter/TorFAQ#WhydoweneedPolipoorPrivoxywithTorWhichisbetter
|title=TheOnionRouter/TorFAQ |work=Tor Project |access-date=28
December 2010}}</ref> -->

<ref name="torproject-rumors-exaggerated">{{cite web
|url=https://blog.torproject.org/blog/rumors-tors-compromise-are-greatly-exaggerated
|title=Rumors of Tor's compromise are greatly exaggerated |last=phobos
|website=Tor Project |date=24 October 2011 |access-date=20 April 2012
|archive-date=30 January 2012
|archive-url=https://web.archive.org/web/20120130020255/https://blog.torproject.org/blog/rumors-tors-compromise-are-greatly-exaggerated
|url-status=live }}</ref>

<ref name="torproject-sponsors">{{cite web
|url=https://www.torproject.org/about/sponsors.html.en |title=Tor:
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<ref name="torstatus">{{cite web
|url=https://metrics.torproject.org/networksize.html |title=Tor Server
Status |publisher=Tor Project - Metrics |access-date=7 July
2021}}</ref>

<ref name="tp-blacklisting">{{cite web
|url=http://threatpost.com/tor-begins-blacklisting-exit-nodes-vulnerable-to-heartbleed/105519
|title=Tor begins blacklisting exit nodes vulnerable to Heartbleed
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|access-date=28 April 2014 |archive-date=19 April 2014
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<ref name="twe-zmap">{{cite
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<ref name="usenix-bad-apple">{{cite conference
|url=https://www.usenix.org/events/leet11/tech/full_papers/LeBlond.pdf
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<ref name="verge-applebaum">{{cite web
|url=https://www.theverge.com/2013/3/11/4091186/interview-uncut-jacob-appelbaum
|title=Interview uncut: Jacob Appelbaum |author=Sirius, R. U.
|website=theverge.com |date=11 March 2013 |access-date=17 September
2017 |archive-date=20 October 2014
|archive-url=https://web.archive.org/web/20141020223354/http://www.theverge.com/2013/3/11/4091186/interview-uncut-jacob-appelbaum
|url-status=live }}</ref>

<ref name="wired-fbi-controlled">{{cite magazine
|url=https://www.wired.com/threatlevel/2013/09/freedom-hosting-fbi/
|title=FBI Admits It Controlled Tor Servers Behind Mass Malware Attack
|first=Kevin |last=Poulsen |magazine=[[Wired (magazine)|Wired]]
|date=13 September 2013 |access-date=22 December 2013 |archive-date=21
December 2013 |archive-url=https://web.archive.org/web/20131221024649/http://www.wired.com/threatlevel/2013/09/freedom-hosting-fbi/
|url-status=live }}</ref>

<ref name="wired-feds-are-suspects">{{cite magazine
|url=https://www.wired.com/2013/08/freedom-hosting/ |title=Feds Are
Suspects in New Malware That Attacks Tor Anonymity |first=Kevin
|last=Poulsen |magazine=[[Wired (magazine)|Wired]] |date=8 May 2013
|access-date=29 April 2014 |archive-date=29 April 2014
|archive-url=https://web.archive.org/web/20140429202100/http://www.wired.com/2013/08/freedom-hosting/
|url-status=live }}</ref>

<ref name="wired-rogue-nodes">{{cite news
|url=https://www.wired.com/politics/security/news/2007/09/embassy_hacks?currentPage=all
|title=Rogue Nodes Turn Tor Anonymizer Into Eavesdropper's Paradise
|first1=Kim |last1=Zetter |author-link=Kim Zetter |newspaper=[[Wired
(magazine)|Wired]] |date=10 September 2007 |access-date=16 September
2007 |archive-date=31 December 2008
|archive-url=https://web.archive.org/web/20081231175940/http://www.wired.com/politics/security/news/2007/09/embassy_hacks?currentPage=all
|url-status=live }}</ref>

<ref name="wp-feds-pay">{{cite news
|url=https://www.washingtonpost.com/blogs/the-switch/wp/2013/09/06/the-feds-pays-for-60-percent-of-tors-development-can-users-trust-it/
|title=The feds pay for 60 percent of Tor's development. Can users
trust it? |first=Brian |last=Fung |work=The Switch
|publisher=Washington Post |date=6 September 2013 |access-date=6
February 2014 |archive-date=9 September 2013
|archive-url=https://archive.today/20130909202619/http://www.washingtonpost.com/blogs/the-switch/wp/2013/09/06/the-feds-pays-for-60-percent-of-tors-development-can-users-trust-it/
|url-status=live }}</ref>

<ref name="wsj-anonymous-contraversial">{{cite news
|url=https://www.wsj.com/articles/SB10001424127887324677204578185382377144280
|title=Tor: an anonymous, and controversial, way to web-surf
|first=Geoffrey A. |last=Fowler |work=[[Wall Street Journal]] |date=17
December 2012 |access-date=19 May 2013 |archive-date=11 March 2015
|archive-url=https://web.archive.org/web/20150311064250/http://www.wsj.com/articles/SB10001424127887324677204578185382377144280
|url-status=live }}</ref>

<ref name="wu8-ubuntu-ppa">{{cite web
|url=http://www.webupd8.org/2013/12/tor-browser-bundle-ubuntu-ppa.html
|title=Tor Browser Bundle Ubuntu PPA |first=Andrei |last=Alin
|website=Web Upd8 |date=2 December 2013 |access-date=28 April 2014
|archive-date=21 April 2014
|archive-url=https://web.archive.org/web/20140421220450/http://www.webupd8.org/2013/12/tor-browser-bundle-ubuntu-ppa.html
|url-status=live }}</ref>

<ref name="xakep-whole-hog">{{cite web
|url=http://eng.xakep.ru/link/51074/ |title=Включаем Tor на всю
катушку |trans-title=Make Tor go the whole hog |first=Антон
|last=Жуков |website=Xakep |date=15 December 2009 |access-date=28
April 2014 |url-status=dead
|archive-url=https://web.archive.org/web/20130901035137/http://eng.xakep.ru/link/51074/
|archive-date=1 September 2013 }}</ref>

<ref name="arrests">{{Cite news
|url=https://www.bbc.co.uk/news/technology-29987373 |title=Dark net
experts trade theories on 'de-cloaking' after raids |date=7 November
2014 |access-date=12 November 2014 |newspaper=BBC News |last1=Lee
|first1=Dave |archive-date=12 November 2014
|archive-url=https://web.archive.org/web/20141112165655/http://www.bbc.co.uk/news/technology-29987373
|url-status=live }}</ref>

<!--ref name=technologyreview>{{cite news |title=Home Internet with
Anonymity Built In |first=Tom |last=Simonite
|url=http://www.technologyreview.com/web/26981/?a=f
|newspaper=[[Technology Review]] |date=22 December 2010
|access-date=14 May 2011}}</ref-->

<ref name="tor-gitlab-repoanalytics">{{cite web
|url=https://gitlab.torproject.org/tpo/core/tor/-/graphs/main/charts
|title=Repository Analytics |website=Tor Project GitLab
|access-date=24 August 2022 |url-status=live }}</ref>

}}

== General and cited references ==
{{Refbegin}}
* {{Cite book |title=Computer Privacy Handbook |first=Andre
|last=Bacard |isbn=978-1-56609-171-8|date=1 January 1995 }}
* {{cite journal |last1=Lund |first1=Brady |first2=Matt
|last2=Beckstrom |date=2021 |title=The Integration of Tor into Library
Services: An Appeal to the Core Mission and Values of Libraries
|journal=Public Library Quarterly |volume=40 |issue=1 |pages=60–76
|doi=10.1080/01616846.2019.1696078 |s2cid=214213117 }}
* {{Cite book |title=Understanding the Usage of Anonymous Onion
Services: Empirical Experiments to Study Criminal Activities in the
Tor Network |first=Juha |last=Nurmi |isbn=978-952-03-1091-2 |date=24
May 2019 }}
* {{Cite book |title=Applied Cryptography |first=Bruce |last=Schneier
|author-link=Bruce Schneier |isbn=978-0-471-11709-4|date=1 November
1995 }}
* {{Cite book |title=Email Security |first=Bruce |last=Schneier
|author-link=Bruce Schneier |isbn=978-0-471-05318-7 |date=25 January
1995 |url-access=registration
|url=https://archive.org/details/emailsecurityhow0000schn }}
{{Refend}}

==External links==
{{Commons category|Tor project}}
* {{Official website}}
* [http://freehaven.net/anonbib/ Anonymity Bibliography]
* [https://2019.www.torproject.org Old website]
* [https://web.archive.org/web/20171220172642/https://www.torproject.org/getinvolved/mirrors.html.en
Archived: Official List of mirror websites]
* [https://www.youtube.com/watch?v=JWII85UlzKw&index=1&list=PLwyU2dZ3LJErtu3GGElIa7VyORE2B6H1H
Animated introduction]
* [https://media.ccc.de/v/31c3_-_6112_-_en_-_saal_2_-_201412301715_-_tor_hidden_services_and_deanonymisation_-_dr_gareth_owen
Tor: Hidden Services and Deanonymisation] presentation at the 31st
Chaos Computer Conference
* [https://torflow.uncharted.software/ TorFlow], a dynamic
visualization of data flowing over the Tor network
* [https://media.ccc.de/v/32c3-7322-tor_onion_services_more_useful_than_you_think
Tor onion services: more useful than you think] in a 2016 presentation
at the 32nd Annual [[Chaos Communication Congress]]
* [https://www.youtube.com/watch?v=xGIE7KTJiBY A core Tor developer
lectures at the] [[Radboud University Nijmegen]] in The Netherlands on
anonymity systems in 2016
* [https://web.archive.org/web/20161019151220/https://people.torproject.org/~isis/slides/2016-10-13-waterloo-handout.pdf
A technical presentation given at the] [[University of Waterloo]] in
Canada: Tor's Circuit-Layer Cryptography: Attacks, Hacks, and
Improvements
* [https://www.youtube.com/watch?v=ShrZ4B9R3NQ A Presentation at the
March 2017 BSides Vancouver Conference on security practices on Tor's
hidden services given by] [[Sarah Jamie Lewis]]

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