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How The NSA Uses Social Network Analysis To Map Terrorist Networks

2013 June 12

Ever since The Guardian reported that the National Security Agency (NSA) has been collecting the phone record metadata of millions of Americans, the cable talk circuit has been ablaze with pundits demanding answers to what should be obvious questions.

Who knew about the program to collect data? (Apparently, all three branches of government). Who else has been supplying data?  (Just about everybody, according to the Washington Post). What is metadata?  (It’s data about data).

The question that nobody seems to be asking is probably the most important one:  What is the NSA doing with the data and why do they need so much of it?  The answer is a relatively new field called social network analysis and, while it may make people uneasy, the benefits far outweigh the risks, so it is probably something we will just have to accept.

The New Science of Networks

The story of networks starts in 1736, long before the United States became a country, when Leonhard Euler set out to conquer a famous math problem concerning the Seven Bridges of Königsberg. To solve it, he created a new form of mathematics called graph theory, which concerned itself with links and nodes in a network.

In the 1950’s, interest renewed in Euler’s networks.  First, Anatol Rapoport introduced the concept of triadic closure, which asserted that networks grow when people meet through a central friend that they both know.  Later, Erdős and Rényi showed that as networks got bigger, communication among the people in the network got much more efficient.

In the 1970’s a sociologist named Mark Granovetter argued that we get most of our information not through close friends, but through weak ties and in the 1990’s Watts and Strogatz built on Granovetter’s work by showing that small clusters of people naturally organize themselves into far flung networks.

So by the late 1990’s, the small field of network analysis had built into a full fledged science and it was about to be applied to an increasingly important problem:  Terrorist networks.

Mapping Terrorist Networks

Valdis Krebs of Orgnet is a network scientist who in 2002 published a widely praised paper on mapping terrorist networks and has since consulted with the Defense Department on methods and approaches of evaluating and dismantling terrorist organizations.

While he isn’t privy to classified information, he describes on his website how an entire network can be mapped using commercially available software by identifying two initial suspects:

Two terrorists step_0

It used to be that law enforcement officers would simply watch the two men closely, but in the era of global jihad, that’s much too slow to save lives.  The two might be peripheral to the conspiracy and it could take years before you could connect them to the leadership of the network, if ever.

Here’s where the data from Verizon and other companies comes in.  If you can analyze communication records, you can move much more quickly.  However, you don’t want to look at everyone the suspects talk to because you’ll end up with mostly incidental contacts, like friendly neighbors and delivery men.

But if you kept Rapoport’s concept of triadic closure in mind and had full access to communication records, you could look for contacts the two suspects have in common and start to build out a map of the conspiracy.

step_1 small terrorist network

The next step would be to analyze the contacts of the suspects’ connections, again looking for closed triads within the existing network.  As you progress from link to link, a fuller picture begins to form (click to enlarge).

  step_2 large terrorist network

Once you have the network mapped, you can begin to mathematically analyze it, which is how important insights can be gleaned even before wiretapping and surveillance warrants have been issued.

You can, for example, assess who is well integrated into the network by calculating who is most central; who has the widest reach by counting how many people in the network are within two connections from them and who in the network provides a crucial role as a bridge between otherwise unconnected people (as Mohamed Atta, the uppermost green node, does in the 9-11 network above).

The result is an almost uncannily accurate picture of the leadership, who can then be targeted to dismantle the network. (It has been estimated that the 9-11 network could have been broken up if just three central nodes had been taken out).

Network Metrics

It should be clear by now why the government regards access to communication records as so crucial to national security.  If the system had been in place in 2001, there is a high probability that the 9-11 network would have been broken up, saving thousands of lives and trillions of dollars.

It would be impractical, to say the least, to get court orders for each and every connection a suspect has, most of whom would not even be investigated. Without a full data set, the social network analysis could not be done and more intrusive, but less efficient methods, would need to be employed.

So whatever you might think of the program, it is most probably here to stay. What is perhaps of greater concern is that this type of analysis is not unique to antiterrorism, but is increasingly becoming a basic fact of commercial life.

Beyond the cell phone companies, social networks like Facebook, Google+ and Twitter can analyze the communications of hundreds of millions of people.  Retail giants like Amazon, Walmart and Target are sifting through our purchases in order to predict our future behavior.

Wherever we go, our movements, faces and actions are being analyzed and, more often than not, it is not the government.

The truth is that there is a dark side to technology and our privacy is being breached every day by someone, somewhere.  That’s just a fact of modern day life.  It seems to me that if we’re willing to accept it from marketers who are trying to to sell us goods and services, we should be able to tolerate it from those who are trying to protect us.

– Greg

Note:  Special thanks for Valdis Krebs of Orgnet for supplying the network maps, calculations and consultation for this post.

13 Responses leave one →
  1. Alistair McMillan permalink
    June 12, 2013

    Recently, a news article carried the headline: “Did you really think Google was on your side?” Wrong question. The right one is whether they – or anyone else (government, CIA, google, internet user, whistleblower, whoever) is on the side of according the broader public their rights to freedom, security and is prepared to be sufficiently transparent about any of their activities which may affect another person or group of people. Google is a business; their motive is profit, and as long as they make it legally AND ethically, that’s fine. Government should ensure that the laws and practices of business and their own agencies are ethical, but every government necessarily has secrets – they must have because of the nature of politics. Whether their secrets are sinister (eg. an operation to poison an an outspoken critic) or ethically and morally correct (eg. an operation to covertly uncover a terrorist plot dangerous to thousands of innocent people) is the question. It is not yet a proven fact that any of the information they may have access to has been abused. And what is the big deal about the government having potential access to your personal information when you are not committing a crime and aren’t involved in anything ethically or morally wrong, in the light of the terrorist threat who WILL abuse their rights to freedom, who WILL endanger others’ liberties?

    However, I say, while the guy who leaked the info about PRISM hasn’t done the world a great deal of good thereby, he is neither a hero or a villain. I don’t think the National Security agencies are doing themselves or anyone any favors by sticking to their line that he has broken laws and must pay. The fact that they have apparatus in place to secure the US does not need to be secret. The fact that they were conducting surveillance on communications was already widely known, and my guess is that terrorists will simply now find ways to communicate that can’t be tracked, which is a blow to security – but also makes it more difficult for the terror network to operate efficiently.

    I think we all need to take a step back, stop throwing tomatoes at each other, and remember who the real enemy is.

  2. June 12, 2013


    Some good points. However, I do think there is a problem with the government listening in on private conversations and strongly believe that digital privacy is a very important issue (and wrote about some of the dangers here).

    I think the salient point about the NSA program is how restrained and reasonable it is (at least as its been reported). It basically seems to be used to zero in on people whose privacy needs to be violated rather than violating everyone’s privacy in the name of security. It also has congressional and judicial oversight. All in all, it appears that everything is being done by the book.

    And that’s what’s important. What you don’t want is a small group of people going off on a flyer and making their own rules. If we don’t like the rules, we can change them. If people are free to break the rules, we truly have no protection.

    – Greg

  3. Neno permalink
    June 14, 2013

    is this a re-post?

    haven’t you post this already?

  4. June 14, 2013

    It was previously posted on There is some overlap between my column there and my personal blog and I’m contractually obligated to a short embargo period before I post here.

    – Greg

  5. Alistair McMillan permalink
    June 14, 2013

    Thanks for the reply Greg. Agreed, we never know which direction a government or agency will take in future, and we need safeguards in place to make sure they don’t abuse their power, also agreed that they currently seem to be acting within their mandate.

  6. Neno permalink
    June 16, 2013

    I was thinking on Krebs’ paper.
    pretty sure I read it here first.

    anyway, doesn’t matter.

    great post as usual.

    keep ’em coming.

  7. June 16, 2013

    I think that was an earlier paper. I just spoke to him about this one last week.

    In any case, Valdis provides a great, easy to understand overview of social network analysis on his site. If you’re interested in SNA, you should check it out:

    – Greg

  8. July 23, 2013

    This last bit sums it up:

    “It seems to me that if we’re willing to accept it from marketers who are trying to to sell us goods and services, we should be able to tolerate it from those who are trying to protect us.”

    They are the same scenarios yet people react so harshly towards one.

    Well written. I for one, have no problems with it. Having problems with one but not the other is contradictory.

  9. July 23, 2013

    Very true. Personally, I think we should be cautious about both, but not to the point of hysteria.

    – Greg

  10. Alastair McGowan permalink
    March 16, 2015

    From the moment I knew govts wanted to retain communication data ten years ago I knew that SNA and related analyses would be the prime methods. My perspective on this has been that governments seem very reluctant to constrain the use of these methods to terrorism and the mafia. In other words they want to keep open the possibility of using it more broadly. And that is my concern, that the function creep and public acceptance keeps going until we find ourselves in a world where government and corporate entities map and categorise all of us according to whatever criteria they choose. 1984 and very little between here and there.

  11. March 17, 2015

    I see your point Alistair, but social network analysis is one of the most benign forms of surveillance. It’s fairly difficult to come up with a false positive and becomes more so as the network becomes more complete (the bigger the network, we’d have to have ore and closer connections to look suspicious). There are, however, good reasons to worry about digital technology, some of which I discussed here.

  12. jon surge permalink
    April 2, 2016

    Oddly the rights of artificial legal entities seem to have more legal rights as “persons” than I. I am an actual person, yet this article mistakenly argues corporations and governments have more rights than I. I can not opt out of all this surveillance even though I highly value my privacy and am a peaceful, innocent party.

    This is moral outrage, an ethically legally unjust an affront to all human beings. However, so many journalists uncritically, simply mentally shrug pretending as if there is no demeaning quality to the respect and dignity an actual human being deserves. Government and these corporate entities did not decide my conception, birth, talents, etc. They should be required to seek my permission. This highlights the corruption endemic to our government and I believe is unconstitutional.

    This is another piece of poorly thought out propaganda demeaning humanity made in the Creator’s image with unalienable rights.

  13. April 2, 2016

    Thanks for sharing your thoughts Jon.

    – Greg

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