There are better ways for NSA to root out terrorists.

• Author: Cohen, Elliot D.
• Position: National Security Agency's Mass Warrantless Surveillance Network - National Affairs

THE PUBLIC perception of the National Security Agency (NSA) surveillance program, the one promulgated by government, largely has been that of a set of protocols fine-tuned to the task of preventing terrorist attacks. However, less is known about the true nature of NSA data searches, their limitations, faults of the technology, and the comparative value of less high-tech investigative techniques.

The question of how efficient the Mass Warrantless Surveillance Network (MWSN) is, or how well its technologies work, can be understood in terms of how accurate it is, which, in this context, means what percentage of the time it correctly identifies someone as a terrorist. However, for every such "true positive" the system returns, there also are a vast number of "false positives"--that is, numerous cases of falsely identifying someone as a terrorist. This is the problem of false positives, and it permeates the entire MWSN.

One salient instance of the situation is the use of pattern-matching searches with upstream programs to identify terrorists. This particular type of search involves construction of algorithms that look for behavior patterns associated with a specific target group. In commercial advertising, this means creating a profile of prospective consumers who are most likely to be interested in a product that is being marketed.

For instance, a magazine about hunting would attempt to target a demographic population that most likely would be interested in going hunting. Thus, according to a report of the Fishing and Wildlife Service, the most likely hunters would be white males between the ages of 55 and 64, living in rural regions of the Southeast, with annual incomes between $50,000 and $100,000. Given that 5.7% of the U.S. population hunts, targeting this group would make it more likely to reach prospective subscribers--but, even so, such bulk behavioral advertising tends to have a relatively low, single-digit positive response rate. This means that the false positives occur in the 90% range.

However, it is not as easy to create a demographic of prospective terrorists as it is of prospective hunters. Indeed, in contrast to individuals who go hunting, there have been relatively few terrorist attacks on the U.S. that enable construction of a terrorist demographic. Consequently, the pattern searches for prospective terrorists typically take an indirect approach. This involves looking for anomalous Internet communication patterns; that is...