Can Super Crunching Help Find Terrorists?

Ian Ayres

An important part of the multipronged attack against the use of torture is the claim that torture does not produce useful information. We don’t even have to consider the barbaric costs to our integrity, if the practice doesn’t produce any benefits.

But it’s not clear that the same “no benefit” argument can be said about data mining the phone records of the “community of interest” surrounding investigative targets.

The NY Times reported yesterday that national security letters sometimes went beyond asking for information on the calls of targets by including the sentence:

“Additionally, please provide a community of interest for the telephone numbers in the attached list.”

The article explained that community of interest data “might include an analysis of which people the targets called most frequently, how long they generally talked and at what times of day, sudden fluctuations in activity, [and] geographic regions that were called.”

The Times’ spin is that this technique exponentially increased the breadth of the judicially unsupervised data collection.

But frankly, it’s still unclear what was being done. The article says that the community of interest analysis:

was limited to people and phone numbers “once removed” from the actual target of the national security letters.

So it is not clear whether the technique was limited to “an analysis of which people the target most frequently called” or whether it also analyzed the people that these “once removed” people called. Since the national security letters sometimes included groups of telephone numbers, they may have also asked if the “once removed” people of target A ever communicated with the “once removed” people of target B. It’s easy to think of reasons why there might be false positives with such connections (e.g., both people might have called the same dry cleaner). But these connections can also be valuable.

I know because I’ve used it myself.

A couple of years ago, my cell phone was stolen. I hopped on the Internet and downloaded the record of telephone calls that were made both to and from my phone. This is where "community of interest" analysis came into play. The thief made more than a hundred calls before the service was cut off. Yet most of the calls were to or from just a few phone numbers. The thief made more than thirty calls to just one phone number, and that phone number had called into the phone several times as well. When I called that number, a voice mailbox told me that I’d reached Jessica’s cell phone. The third most frequent number connected me with Jessica’s mother (who was rather distraught to learn that her daughter had been calling a stolen phone).
It became clear that the thief was Jessica's boyfriend.

Not all the numbers were helpful. The thief had called a local weather recording a bunch of times. By the fifth call, however, I found someone who said he’d help me get my phone back. And he did. A few hours later, he handed it back to me at a McDonald’s parking lot. Just knowing the telephone numbers that a bad guy calls can help you figure out who the bad guy is. In fact, cell phone records were used in just this way to finger the two men who killed Michael Jordan’s father.

Valdis Krebs used network analysis of public information to show that all nineteen of the 9/11 hijackers were within two email or phone call connections to two al-Qaeda members who the CIA already knew about before the attack. Of course, it’s a lot easier to see patterns after the fact, but just knowing a probable bad guy may be enough to put statistical investigators on the right track.

The 64,000 terabyte question is whether it’s possible to start with just a single suspect and credibly identify a prospective conspiracy based on an analysis of social network patterns.

None of this is to say that datamining should be conducted without much more judicial oversight. But it is to say that the potential benefits of Super Crunching -- even of people who are trying to cover their electronic tracks -- stand on a firmer footing than torture.
Posted 7:39 AM by Ian Ayres [link]