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Tools for Rendering Censorship Firewalls Ineffective
by Bill Stewart 17 Dec '03

17 Dec '03

I've been trying to categorize the web censorship techniques available to governments, such as Singapore and China's Firewall Curtains, Germany's ISP Threats, etc. The objective is to make information widely and conveniently available to subjects of the censoring country by building tools that will provide multiple paths to data that are easy to find and hard to block because they're too pervasive. I'm assuming that email is difficult to block, in-country public websites are blockable (through business licenses, lawsuits, rubber-hoses, or confiscation), in-country private websites are difficult to block but not very relevant, authors can afford and post to foreign web sites without effective blocking, and that the real "threat" to the government is foreign websites making banned information conveniently available to its subjects. I'm also assuming that the government can use humans to discover a moderate quantity of banned info, but that blocking will mostly be done by bots rather than human readers. In particular, I'm ignoring the approach of in-country hidden websites, since it's too vulnerable in some countries, and focussing on the web rather than email because it's mass-market and easier to use, and email is harder to stop, especially given crypto and remailers. Notation: "Attack" is the Censors trying to stop data; "defend" and "evade" are the Good Guys trying to not get censored. The obvious techniques I can see include 1) Filter on IP address (e.g. German attack on XS4ALL) 2) Filter on DNS Name 3) Filter on Patterns in URL 4) Filter on Patterns in PUT/GET Requests 5) Filter on Patterns in Response. 6) Traffic Analysis on reading patterns Defenses - The most important defenses to these attacks depend on ubiquity and volume - they can block one or two of anything, they might be able to block a thousand, and it's not possible to block millions of things everywhere. So building bridges between systems and increasing multiplicity is a win. 1) It's easy to evade the crude version of this attack - use rolling IP addresses, and use DNS to publish the new ones. For the German model, where the government has to tell the ISPs who to block, this wins. They can counter by blocking your whole IP network, not just a single machine, which you can counter by hopping IP networks as well as hosts, though that's more trouble (and blocking routes is probably easier than blocking hosts, since you do it at the routers, and harder to get people to turn back on.) They can also enforce boycotts on the ISP, as they did with XS4ALL - blocking most of the traffic to a site can affect its other traffic enough to be economically annoying. The attackers can counter by also tracking the address with a bot - if you change addresses hourly, they can change blocking addresses hourly, which may workable for somewhere high-tech like Singapore or very focussed like China, but isn't very effective for somewhere porous like Germany that has a system of laws that move at the speed of bureaucracy. A very effective defense against this method is to deploy relay servers, either anonymizers or simple non-anonymizing cgi scripts that take URLs like http://foo.bar.com/cgi-bin/relay.pl/http://banned.site.org/ and fetch and return the real URL (perhaps modifying any URLs in it to connect through the relay.) This works if there are lots of easy-to-find relay servers. An obvious approach would be to package the relay program with Apache or other popular web server, so anybody who didn't bother turning it off would have a relay named "relay.pl"; the attackers can't realistically block everybody who's got one. Another effective defense is to use web servers that gateway to AFS (Andrew File System) or other distributed file systems. This lets /stanford.edu/censored-mirrors/banned.html be accessible from any site supporting AFS, such as http://www.cmu.edu/afs/stanford.edu/censored-mirrors/banned.html This has the great advantage that AFS sites are usually at major universities, which are important enough that lots of people would complain if you blocked them. This works better if there's an easy way to insert things into the AFS tree - volunteers are fine, but if there are servers that can automatically import material it becomes easier, either by copying or by various kinds of indirection. (On the other hand, if you allow automated import, attackers can turn your site into the Child Pornography NarcoTerrorist Bomb Info Mart and ban you...) Do the major web crawlers index AFS? Or do the sites use robots.txt to prevent multiple crawls, e.g. by only allowing searching on the local file systems and not on the remote ones? 2) Filtering on DNS names is an attack that proxy servers can use - the HTTP spec [RFC1945] says that requests to proxies need to send an Absolute URI (method://machine[:port][abs_path]) rather than just the absolute path (/etc.), so the proxy servers can filter on DNS names, defeating the rolling-IP-address defense. Doesn't stop relays. Non-proxy attacks don't have access to this method. However, governments that use full-scale firewalls and not just http proxies can also restrict what DNS queries the National DNS Servers will pass. How to defend against it for non-proxy attackers? One way is to make it easy to find the IP address of a server with banned material - web indexers can find everything, so putting the IP form of the URL in a file that the popular indexers, along with useful keywords, is one way to make sure you get found. Another would be to deploy DNS servers widely (done:-) and maybe form-based interfaces for users that will run Dig or whatever. 3) Filtering on patterns in URLs - as with DNS filters, a proxy server run by an attacker can block access based on patterns in the URL, such as relay.pl. This makes it tougher to use relays as a defense, because they either need to have different names on different machines (harder for users to find and for administrators to implement without having to pay attention), or else to not need a name (either modify the protocols or at least the servers so that http://foo.bar.com/http://banned.site.org/stuff.html gets handled properly.) The latter is doable, but probably requires more administrator support? Pattern matching on URLs can make it easier to attack AFS - you don't need to kill the whole AFS tree, just the banned parts. Pattern matching on URLs already starts to have heavy volume issues - can a proxy server take the extra time to search an ever-larger banned list on every web hit? Having used overloaded proxy servers at work (:-), I'd expect the population to start acting like disgruntled postal workers if the mandatory national firewall is underpowered. On the other hand, I suppose a government could partially solve scale problems by requiring a license fee for use of the proxy server; a few bucks per user could pay for increasing numbers of servers as well as tracking who's reading what. 4) Filter on Patterns in PUT/GET Requests As a defense against blocking URLs by patterns, defenders can send requests as message-body in PUT/GET requests; this is also useful for submitting banned material to cooperative sites. Attackers can filter on this material, though they can't easily filter out SSL or S-HTTP requests by content, depending on how much the protocols pass material end-to-end rather than link-by-link where the proxy can see it. 5) Filter on Patterns in Responses. Similarly, attackers could just grep for banned material in HTTP responses, though SSL/S-HTTP both interfere with this. Defenders can also structure banned writing in ways that don't trigger patterns easily (e.g. don't refer to Lee Kwan Yew, just refer to That Bum or Mr. Big, etc.) Filtering on picture content is obviously difficult, so including text in graphics can help prevent attacks. In general, I'd expect filtering attacks to be extremely susceptible to volume. On the other hand, attackers don't have to filter in real-time; they could scan material as a background activity, and go arrest the people who have received contraband after the fact, or just block their National Firewall Passports if they're reading too much. In general, this attack is probably more useful for overall study of what their subjects are reading than for real-time. 6) Traffic Analysis - who's reading what? Where? Who's reading a lot of contraband? What's popular foreign material? Which of the attackers' subjects are possible fellow travellers, based on what they're reading? This kind of material is useful for marketing as well as for identifying malcontents - businesses aren't always pro-privacy either, though they want their own secrets kept secret. Many of the attacks above can work as after-the-fact analysis more effectively than they can as real-time blocking, and volume is less of a problem for crunching a sample of firewall logs than for active blocking; this may be the hardest attack to counter, though it's repression rather than censorship. If you can't police everybody, you can at least encourage the policeman in everybody's head. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ What other kinds of attacks are there? What other defenses? What kinds of holes are there in these defenses? # Thanks; Bill # Bill Stewart, +1-415-442-2215 stewarts(a)ix.netcom.com # <A HREF="http://idiom.com/~wcs"> # You can get PGP software outside the US at ftp.ox.ac.uk/pub/crypto

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GCHQ releases Venona files (from UK Telegraph)
by Sherry Mayo 17 Dec '03

17 Dec '03

Hi all, A couple of articles from the UK Daily Telegraph may be of interest. The earlier one "Codebreakers come clean" is about the upcoming congference on cold war intelligence & mentions the continued release of the NSA's Venona files (see http://www.nsa.gov:8080/docs/venona/venona.html) The article is at: http://www.telegraph.co.uk/et/access?ac=116192744309&pg=//96/9/29/wspy29.ht… The second is about the GCHQ (UK equivalent of NSA) releasing its own Venona files in response to the NSA release. http://www.telegraph.co.uk/et/access?ac=116192744309&pg=//96/9/30/ngch30.ht… These are being released into the public records office, but there is no indication that they will appear on the net for the time being. Sherry

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A periodic alert regarding Tim May
by Bovine Remailer 17 Dec '03

17 Dec '03

Tim May styles his facial hair to look more like pubic hair.

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Re: [AP] Afghanistan
by Wayne H. Allen 17 Dec '03

17 Dec '03

At 05:57 PM 9/29/96 EDT, Dr.Dimitri Vulis KOTM wrote: >"Wayne H. Allen" <whallen(a)capitalnet.com> writes: > >> At 04:10 AM 9/29/96 EDT, Dr.Dimitri Vulis KOTM wrote: >> >Afghanis publicly hanged their former president, Najibullah [no last name]. >> >Other countries should follow their example. >> > >> >> And this would accomplish???? And this has what to do with cryptography?? > >Nothing, of course - neither do Timmy May's stupid rants, lies, and personal >attacks. > >By the way, your abuse of your native language suggests that you're probably >a product of U.S. public education. > > And you would be far off base once again. Wayne H.Allen whallen(a)capitalnet.com Pgp key at www.capitalnet.com/~whallen

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Looking for Codebreaker's by David Kahn
by Hendrik Reh 17 Dec '03

17 Dec '03

Im looking for Codebreakers by David Kahn !! Can anybody give me a hint where i can get this book thanx -- ,,,, Gruss, /'^'\ Hendrik ( o o ) -oOOO--(_)--OOOo------------------------------------------------ Hendrik Reh, Tel. : +49 0681 48362 .oooO WWW: http://fsinfo.cs.uni-sb.de/~garetjax/ ( ) Oooo. eMail: hereh(a)stud.uni-sb.de ---\ (----( )------------------------------------------------- \_) ) / (_/

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Re: What about making re-mailers automatically chain?
by Greg Broiles 17 Dec '03

17 Dec '03

>Would it be a good idea to have a re-mailer "randomly" decide whether to >send the mail to the destination or to another re-mailer. No. The remailer user should be presumed to know what s/he wants. Some remailer users may want to optimize for speed and certainty of delivery and therefore use a short chain; other users may want to optimize for more difficult traceability, and consequently choose a long chain. Remailers shouldn't try to rewrite the user's (perhaps) deliberate balancing of these factors. Also, users may choose to use or not use certain remailers based upon their policies, the reputation of the operators, the legal rules affecting the operators, and so forth. These choices should also be left to the user and not overridden by third parties. > If all >re-mailers performed this way, not even the sender would know the path. I don't see why this is useful. As things work now, only the sender knows the path, assuming chaining and nesting encryption. How does taking away the sender's knowledge add security? Adding hops to the chain requires that remailers keep track of other remailers; a robust way of doing this would require that they also keep track of reliability, because deciding to add a downed (or unreliable) remailer to a chain would be harmful. To prevent an active and hostile eavesdropper from adding itself as a remailer eligible to receive extra hops (and then dropping or logging the traffic), this remailer status information should be provided by a trusted source in a secure manner. All of this (adding remailer status tracking based on frequent updates of digitally signed information from a trusted third party) can be done, but it's a pain in the ass to code, and it doesn't add anything that users can't get for themselves. (Users who want long difficult-to-trace chains can already generate them. They can also let software generate random chains at the source.) It also may degrade performance for users who value speed and reliability over untraceability. So I suggest that it's not very useful. The best way to implement this would be to modify remailers to use "Anon-To: random" or "Random-To: xxx(a)yyy.zzz" header commands, such that users who desired the random hop behavior could get it, but users who didn't want it wouldn't get it unexpectedly. (Isn't some remailer doing this already? I've lost track.) -- Greg Broiles | "We pretend to be their friends, gbroiles(a)netbox.com | but they fuck with our heads." http://www.io.com/~gbroiles | |

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Re: GCHQ releases Venona files (from UK Telegraph)
by jya＠pipeline.com 17 Dec '03

17 Dec '03

If anyone in the UK cares to get the GCHQ Venona releases, we'll be pleased to scan them for distribution. Or put them on our Web site. Our fax: 212-799-4003 (US) Vox: 212-873-8700 Or if someone else scans them and needs a Web site, ftp them to: ftp://jya.com/pub/incoming

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Re: Making Remailers Widespread [REMAILERS]
by Bill Stewart 17 Dec '03

17 Dec '03

At 09:37 AM 9/29/96 EDT, you wrote: >How about: maintain a list of trusted blocking-list sites (comparable to the >list of remailers used for chaining) and when it comes the time to update the >local copy of the blocking list, ask a random one on the list; if it's down, >ask another random one on the list. There may even be more than one list. :-) Getting more complex, but it might be workable. >> sender-blocking list ... >With most ISP's it's trivial to forge one's From: header in SMTP. >Switching to another dime-a-dozen throwaway account is also trivial. >Just admit that you can't block senders, and don't pretend that you >can - false pretenses destroy one's credibility. You obviously can't source-block a determined spammer, but you can slow down some spam attacks, especially if they're one individual using his/her regular account. It's no panacaea, but it helps. Also, if you source-block based on patterns anywhere in the header, you can catch less capable email forgers. >I think I see a way to accomplish this without too much trouble. >When an e-mail is directed at u@c4.c3.c2...c1, the code that checks >for blocking will search for the following records in the blocking list: >u@c4.c3.c2...c1 (exact match) >*@c4.c3.c2...c1 (replace user by *) >u@*.c3.c2...c1 (replace leftmost .-separated piece of domain by *) >*@*.c3.c2...c1 (both) >and repeat until there are only 2 components left in the domain name. That'd work. It's clunky, but there's no avoiding clunkiness for this sort of thing, and it does preserve privacy. >Now, the question is, who would be allowed to add records containing >'*' to the blocking list using the cookie protocol? I suggest that it be >one of the contacts listed in Internic's database. postmaster@domain is (ostensibly) guaranteed to exist. The Internic database is an interesting alternative, but for this I suspect postmaster is good enough. There's also the problem that for many domains, where smallcompany.com is virtual on an ISP, the Internic database will generally list someone at the ISP, who probably has no interest in the issue, rather than someone responsible for making decisions about smallcompany.com >Thus a blocking record for cypherpunks(a)toad.com could be added by >anyone listed in toad.com's Internic entry. There's no need for any >Remailer Cabal [tinc] to maintain blocking lists. For destination blocking, I agree that users should be able to block their own stuff as automagically as possible. For source blocking, most of the need is for spams and abusers that have been tracked down (or identify themselves in their postings), and that takes human thought. In particular, spammers are unlikely to block themselves from the remailers (:-), but forgers may try to block legitimate users. >One other suggestion: instead of storing one bit of information (the >address is on the list or not), why not have several flag bits. >E.g., the blocking list could contain records similar to: >hash - e.g. 160-bit SHA >flags - e.g. reserve 32 bits Interesting. I suspect the state of the art would be to collect the bits with a disclaimer that there isn't any code to interpret them :-), but it does let you build a blocking database that's usable as capabilities grow. Any suggestions for flags besides block/allow one-way, block/allow two-way, and max-size? I'm thinking of doing a remailer that instead of sending you a message, it sends you a retrieval cookie and lets you send it back to collect the message; blocking that would be another flag. The other kind of blocking that needs adding is blocking by words in message bodies - the spammer that caused me to shut down my remailer and not bring it back up was posting hate messages with somebody else's name and email signed at the bottom. It only took one or two to generate a flood of flames to the victim, and my current remailer couldn't block any followups. Also, since the spammer wasn't generating the flames himself, his spam slipped under the remailer's spam counter, just as hipcrime's did. This sort of blocking also lets you block things like the hipcrime spam and MAKE MONEY FAST. But it's a much more sensitive problem - anybody who can add things to the body-checking list can start doing real censorship, and it's probably best to leave that to individual operators to block, or at least to turn on by hand rather than default. # Thanks; Bill # Bill Stewart, +1-415-442-2215 stewarts(a)ix.netcom.com # <A HREF="http://idiom.com/~wcs"> # You can get PGP software outside the US at ftp.ox.ac.uk/pub/crypto

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Re: Utah as a Religious Police State
by Deana Holmes 17 Dec '03

17 Dec '03

On 30 Sep 96 at 0:55, Moroni wrote: > I never cease to be surprised by the interest that gentiles show in > working mormon communities while totally neglecting their own failing > areas. <rant on> I never cease to be surprised by Mormon apologists who refuse to look in the mirror at problems in so-called "working Mormon communities." I moved to Utah 2 years ago from Texas. Even though I am nominally Mormon (I haven't been to Church in years), it was still a huge culture shock to me. I think the thing that bugs me the most is the way the political system is dominated by a 500 lb. elephant known as the LDS Church. We Utahns sit in a room with this elephant that eats and s**ts and yet we don't talk about the fact that it's there. This is Utah for you...Utah where during the first legislative session I was here (1995) the legislature spent 42 out of 45 days talking about whether they were going to have tightened ethics laws. Where during the last legislative session (1996) the legislature spent 42 of 45 days discussing what to do about the fact that a few kids in one of the Salt Lake high schools wanted to have a gay/lesbian/straight club. NO MATTER that the schools are horribly overcrowded and that in some elementary grades 40-plus students per classroom is the norm. NO MATTER that teachers are horribly underpaid in a state with California-style costs. NO MATTER that despite a $100 million surplus the governor and the legislature can't see clear to get rid of the sales tax on *food*. NO MATTER that if anything terribly controversial (or even not so controversial) comes up, someone in the legislature feels like they have to sound out the Church to make sure that they don't cross Gordon B. Hinckley or Boyd K. Packer and endanger their Church membership. In the meantime, our legislators (with Church approval, these are Church "callings") run down to the prison at Point of the Mountain to "counsel" convicted child abusers and then pass laws to get rid of minimum mandatory sentencing. The roads are falling apart here, the schools are overcrowded. Gang violence is prevalent up and down the Wasatch Front. I heard about a gang-related murder in Layton last weekend. Up until a month ago, when the mayor of Salt Lake City closed the place and forced them out, there was a well-known open-air drug supermarket going on in Pioneer Park. Legislative leaders think that they're above the Open Meetings law. And liquor laws still are pretty backwards. (Gee, just last week places that sell beer actually got permission to put signs that say "BEER" instead of "BEE?" on their premises.) Thing is, Utah is generally a wonderful place to live. As I said, I used to live in Texas. It's great to live in a place where the economy is booming and there are jobs available. The crime rate is pretty low for an urban community (but there are sore spots, as I indicated above). The scenery is downright spectacular. And Salt Lake City proper is a pretty cool place. But I don't believe that Utah is immune to the problems that beset other cities. One thing that would help is for Utah opinion-makers to admit that not everyone who lives in this "pretty, great state" is a devout Mormon and/or a Republican. Not everyone shares the same values as the dominant religion, and they shouldn't have to. I apologise to the cypherpunks mailing list for this rant, but not everyone in Utah agrees with the view expressed by Moroni above. Deana Deana M. Holmes April 1996 poster child for clueless $cientology litigiousness alt.religion.scientology archivist since 2/95 mirele(a)xmission.com

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ADJ_ust
by jya＠pipeline.com 17 Dec '03

17 Dec '03

9-30-96. NYP: "National Security Experts Plan for Wars Whose Targets and Weapons Are All Digital." Is the threat real, or is this just another way to win scarce funds? Military and intelligence officials believe that enemy nations, terrorists and criminal groups either already have the capability to mount information warfare strikes or soon will. Criminals are quickly progressing beyond the vandalism and petty theft associated with teen-aged hackers and into robbery and extortion schemes ranging up to millions of dollars, corporate executives and private investigators say. Others reply that the worst threats mentioned are mostly speculation. "Information warfare is a risk to our nation's economy and defense," said Martin Libicki, a senior fellow at the National Defense University. "But I believe we will find ways to cope with these attacks, adjust and shake them off, just as we do to natural disasters like hurricanes." ----- http://jya.com/adjust.txt (14 kb) ADJ_ust

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