Telephone metadata can reveal surprisingly sensitive personal information

Rayzer rayzer at
Thu May 19 09:57:46 PDT 2016

Addenda... That ex-used furniture salesman
know whose metadata he's viewing too:

Dec. 2013: “With “marginal effort,” they /(a Stanford graduate student
and friends)/ matched more than 27 percent of the numbers using just
Yelp, Google Places and Facebook … “Between Intelius, Google search and
our three initial sources, we associated a name with 91 of the 100 numbers,”

On 05/19/2016 08:13 AM, Александр А. wrote:
> /
>   Stanford computer scientists show telephone metadata can reveal
>   surprisingly sensitive personal information
> Stanford researchers show that telephone metadata – information about
> calls and text messages, such as time and length – can alone reveal a
> surprising amount of personal detail. The work could help inform
> future policies for government surveillance and consumer data privacy.
> Most people might not give telephone metadata – the numbers you dial,
> the length of your calls – a second thought. Some government officials
> probably view it as similarly trivial, which is why this information
> can be obtained without a warrant.
> A new Stanford study of information gathered by the National Security
> Agency shows that warrantless surveillance can reveal a surprising
> amount of personal information about individual Americans. (Image
> credit: Sergey Nivens / Shutterstock <>)
> But a new analysis
> <>
> by Stanford computer scientists shows that it is possible to identify
> a person’s private information – such as health details – from
> metadata alone. Additionally, following metadata “hops” from one
> person’s communications can involve thousands of other people.
> The researchers set out to fill knowledge gaps within the National
> Security Agency’s current phone metadata program, which has drawn
> conflicting assertions about its privacy impacts. The law currently
> treats call content and metadata separately and makes it easier for
> government agencies to obtain metadata, in part because it assumes
> that it shouldn’t be possible to infer specific sensitive details
> about people based on metadata alone.
> The findings, reported today in the /Proceedings of the National
> Academy of Sciences/, provide the first empirical data on the privacy
> properties of telephone metadata. Preliminary versions of the work,
> previously made available online, have already played a role in
> federal surveillance policy and have been cited in litigation filings
> and letters to legislators in both the United States and abroad. The
> final work could be used to help make more informed policy decisions
> about government surveillance and consumer data privacy.
> The computer scientists built a smartphone application that retrieved
> the previous call and text message metadata – the numbers, times and
> lengths of communications – from more than 800 volunteers’ smartphone
> logs. In total, participants provided records of more than 250,000
> calls and 1.2 million texts. The researchers then used a combination
> of inexpensive automated and manual processes to illustrate both the
> extent of the reach – how many people would be involved in a scan of a
> single person – and the level of sensitive information that can be
> gleaned about each user.
> From a small selection of the users, the Stanford researchers were
> able to infer, for instance, that a person who placed several calls to
> a cardiologist, a local drugstore and a cardiac arrhythmia monitoring
> device hotline likely suffers from cardiac arrhythmia. Another study
> participant likely owns an AR semiautomatic rifle, based on frequent
> calls to a local firearms dealer that prominently advertises AR
> semiautomatic rifles and to the customer support hotline of a major
> firearm manufacturer that produces these rifles.
> One of the government’s justifications for allowing law enforcement
> and national security agencies to access metadata without warrants is
> the underlying belief that it’s not sensitive information. This work
> shows that assumption is not true.
> “I was somewhat surprised by how successfully we inferred sensitive
> details about individuals,” said study co-author Patrick Mutchler, a
> graduate student at Stanford. “It feels intuitive that the businesses
> you call say something about yourself. But when you look at how
> effectively we were able to identify that a person likely had a
> medical condition, which we consider intensely private, that was
> interesting.”
> They also found that a large number of people could get caught up in a
> single surveillance sweep. When the National Security Agency examines
> metadata associated with a suspect’s phone, it is allowed to examine a
> “two-hop” net around the suspect. Suspect A calls person B is one hop;
> person B calls person C is the second hop. Analysts can then comb the
> metadata of anyone within two hops of the suspect.
> By extrapolating participant data, the researchers estimated that the
> NSA’s current authorities could allow for surveilling roughly 25,000
> individuals – and possibly more – starting from just one “seed” phone
> user.
> Although the results are not surprising, the researchers said that the
> raw, empirical data provide a better-informed starting point for
> future conversations between privacy interest groups and policymakers.
> For instance, the authors point to the recent shift to reduce the
> metadata retrieval window from five years to 18 months. By drawing
> accurate and sensitive inferences about participants from roughly six
> months-worth of calls and texts, the study suggests that metadata are
> more revealing than previously thought.
> Similarly, the government’s two-hop call sweep was previously three
> hops; that reduction was implemented to reduce the number of people
> caught in a sweep. Shortening the time window could reduce that number
> further, Mutchler said.
> “If we’re going to pick a sweet spot as society, where we want the
> privacy vs. security tradeoff to lie, it’s important to understand the
> implications of the polices that we have,” Mutchler said. “In this
> paper, we have empirical data, which I think will help people make
> informed decisions.”
> The study, “Evaluating the privacy properties of telephone metadata,”
> was coauthored by John C. Mitchell
> <>, the Mary and Gordon
> Crary Family Professor in the School of Engineering, and Jonathan
> Mayer, a scholar in the Stanford School of Engineering and the
> Stanford Law School. Mayer is currently detailed from Stanford to the
> Federal Communications Commission, where he is serving as Chief
> Technologist for the Enforcement Bureau. The project was supported in
> part by the National Science Foundation Team for Research in
> Ubiquitous Secure Technology Research Center.
> **

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