Automated Targeting System (ATS)
In November 2006 the Department of Homeland Security revealed that for years it has assigned "risk assessments" to millions of travelers entering or leaving the country. The Automated Targeting System reviews data from seven large government databases plus the Passenger Name Record data from the airlines. Effectively if you travel internationally ATS creates an instant personal and detailed dossier on you that Customs and Border Protection officers use to decide whether you get to enter the country or will be subject to an enhanced (and potentially invasive) search. The government will retain the data for 15 years. In December 2006 EFF sued DHS to learn more about the invasive unprecedented data-mining system deployed on American travelers.
See EFF's full report for more information.