The Power of Metadata


By Paul RosenzweigThe George Washington University Law School

United States government has collected the telephone records of everybody in the world, including Americans. This was revealed by Edward Snowden, a former National Security Agency subcontractor. The Section 215 metadata-collection program arose from the USA Patriot Act and was signed into law in October 2001. And that is just the start of the story.

A photo of a women using a phone showing the contact's social network as a hologram.
Contact chaining is the practice of retrieving not only the number in question but also all the contact numbers associated with it. (Image: VideoFlow/Shutterstock)

Foreign Intelligence Surveillance Court

The Section 215 metadata-collection program gave rise to an accompanying series of orders issued by the Foreign Intelligence Surveillance Court (FISC). The orders require telephone companies operating in the United States to provide the National Security Agency (NSA) with call detail records.

This is the detailed information of the sort that typically appears on our telephone bill, including the date, time, and duration of a call and the phone number to which the call was placed or received.

As described by the Privacy and Civil Liberties Oversight Board, the Section 215 metadata was to be maintained by the NSA in a centralized database. NSA analysts could search the database with a query, that is an input of a search term, like a phone number—but they may do so only if one of 22 designated NSA officials first determined that the query was based upon a reasonable suspicion that the phone number at issue was associated with terrorism.

This is a transcript from the video series The Surveillance State: Big Data, Freedom, and YouWatch it now, on Wondrium.

Contact Chaining

Once a reasonable articulable suspicion-based search is approved, NSA analysts are allowed to do what is known as contact chaining, that is the practice of retrieving not only the phone numbers in direct contact with the number in question, that’s known as the first hop, but also all the contact numbers associated with the numbers identified in the first hop, including second-hop and even third-hop numbers .

To give you a sense of how large that field of search might become, if one number contacts, let’s say, 100 other numbers and each of those 100 numbers has 100 contacts, now you have 10,000 at the second hop and one million contacts at the third hop.

Learn more about the 1978 FISA legislation.

The Importance of Metadata

Yet the question is why did the government care? Why would it want to know everyone who you call and, inferentially, who you don’t call? Well, it’s impossible to go anywhere in the world without leaving an electronic footprint. And those footprints tell a story.

A photo of Edward Snowden.
The program collecting phone records was revealed by Edward Snowden, a former NSA subcontractor. (Image: Laura Poitras/ Praxis Films/CC BY SA/3.0/Public domain)

To understand why metadata is important, one should study an amusing, but also fascinating, bit of research. It was done by Professor Kieran Healy, who is a sociologist and an associate professor at Duke University, where he’s a member of the Kenan Institute for Ethics. As a sociologist, Professor Healy frequently uses a form of metadata analysis known as social-network analysis.

Social-Network Analysis

Social-network analysis takes information and uses it to construct a map not of a physical geography but of the social geography of a community. In a company, for example, one can find out which employee is the critical linchpin, who routinely shares information between different development groups.

One can also find out which employee is most responsible for creating team spirit and camaraderie. And, of course, the same sort of networking analysis can reveal who is isolated from the group and who doesn’t communicate often with anyone. One can decide who to target for influence and who to ignore.

Indeed, if we can find the one critical member of a social group and influence that person, then we can, for a relatively small amount of effort, influence the entire network. Professor Healy put the idea to work in an interesting and revelatory way.

Uncovering the Network

Professor Healy imagined himself as living in the 1770s, just prior to the American Revolution. And he further imagined that he was a member of the British government, charged with uncovering a network of American conspirators who were secretly plotting a revolt against their lawful king, King George III of England.

Healy speculated how the British might have proceeded if they’d had the sophisticated social network analytical tools available to us today back then. And so he built a social network using data he derived from a book written by David Hackett Fischer about the American Revolution.

A Matrix of Connections

What Hackett had done was collect a form of metadata. in this instance, information about the social memberships of men in Boston. He examined which clubs they belonged to, and which organizing committees they became a part of. Using this data, Healy was able to create a matrix of the connections among Boston revolutionaries.

A portrait of Paul Revere.
According to the social -network analysis, Paul Revere was the person in whom the British ought to have focused their surveillance efforts. Image: Everett Collection/Shutterstock)

Mapping the Social Network

Now, it’s important to know that Healy had no idea what the club members might have been saying to each other in their meetings, or even doing. Healy was doing his analysis more than two centuries after the co-conspirators might have been breathing life into their rebellion and relying only on metadata.

What Healy did know—and what British counter-terrorism specialists might have discovered, with a comparable analysis, was that a sufficiently sophisticated analysis could construct a map of the social network in Boston and would have revealed who were the central figures of Boston male society at the time. The results were fascinating.

The Linchpin

At the center of the social network graph was a single name. And who do you think would be the one person well known to everybody else in the community? And in whom the British would be most likely have to focus their surveillance efforts? It was Paul Revere.

Healy could identify Paul Revere at the center of a suspected rebel plot simply by analyzing who he was socially connected to.

Learn more about three types of surveillance.

The Significance of Metadata

Today through the lens of history that seems obvious to us. But had the British been able to do this analysis back in the revolutionary era, it would have been a revelation.

That is the power of metadata. And it explains, in a nutshell, why the government might be interested in collecting all the records of telephone calls made.

Common Questions about The Power of Metadata

Q: What is social network analysis?

Social network analysis is a kind of metadata analysis. It takes information and uses it to construct a map, not of a physical geography, but of the social geography of a community.

Q: When could the NSA analysts search the centralized database?

The NSA analysts could search the centralized database only if one of 22 designated NSA officials first determines that the query is based upon a reasonable, articulable suspicion that the phone number at issue is associated with terrorism.

Q: What was the idea that Professor Kieran Healy worked on?

Professor Kieran Healy worked on the idea that if we can find the one critical member of a social group and influence that person, then we can influence the entire network.

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