Report calls data-mining expensive, ineffective

The statistical likelihood of false positives is so high that the practice "will inevitably waste resources and threaten civil liberties," according to authors Jim Harper, Cato's information policy studies director, and IBM researcher Jeff Jonas.

Data mining was dubbed a key tool in the war on terror after al Qaeda's attacks on Sept. 11, 2001, with federal agencies arguing that comprehensive monitoring of personal data would assist in tracking terrorists. The method relies on "pattern-based analysis" of private data from large numbers of people, but the technology needed to obtain precise results does not exist, the study found.

"Better interagency information-sharing, investigatory legwork, in pursuit of genuine leads, and better training are what the 9/11 story most clearly calls for," Harper and Jonas argued.