In his New York Times article “Can Network Theory Thwart Terrorists?”, author Patrick Radden Keefe discusses the recent applications of network theory by the CIA and other organizations in order to stop terrorists. Keefe discusses an early network created by Valdis Krebs in which Krebs used shared addresses, telephone numbers, and frequent flier miles to link the 9/11 terrorists. Krebs found that all of the 19 terrorists were tied to one another by just a few links, with a greater amount of links connecting the leader, Mohamed Atta, with the other 18 terrorists. In fact, prior to Krebs’ network, the Army had created an advanced network that sought to map Al Qaeda members and may have succeeded in finding the same disproportionate amount of linkages to Atta, which could have suggested that he was involved in preparation for a future terrorist act.

The decision by the federal government to track data connected to these terrorists raises a complicated question: to what extent should the federal government be allowed to monitor the private data of US citizens? Keefe suggests that this new type of “wire-tapping” – based on linkages in complex networks – bears little resemblance to old-fashioned wiretapping. Whereas old-fashioned wiretapping involved listening in on actual conversation or reading the text of e-mails, the new type of networked wire-tapping is much less invasive; instead of reading the text of an e-mail or listening in on a phone call, computers now track only the sender and recipient of a phone call or message.

But in a world in which most Americans are separated by only six links (verified by network theorist Stanley Milgram), this program has led to an overwhelming amount of “false positives.” In response, intelligence agencies have begun to develop algorithms for determining the “role structure” within a network, searching for differences in the strength of ties among members and attempting to determine a logical hierarchy within a network. While this process is still in its infancy, it represents a powerful method of tracking terrorist groups whose elusive nature has thus far stymied other efforts.