The excellent news weekly, The Week, has a a good one-pager about the National Security Agency, which now has the Congressionally-approved power to conduct warrantless wiretaps.
A system called Echelon screens the flood of information for targeted phrases, names, phone numbers, and addresses, and alerts agents to any matches. In 2003, the NSA had flagged 10 different cell phones used by 9/11 mastermind Khalid Shaikh Mohammed. When his voice matched with one of the numbers, the agency used satellites to triangulate his position and grab him. Ninety-five percent of the raw material collected by the NSA is never translated into intelligible language. But raw data can also be useful. The NSA practices "data mining": analyzing communications for patterns–such as phone numbers being frequently connected with other numbers–that can be revealing even if the content of conversations is not known. Information from the NSA makes up about 75 percent of the president's daily intelligence briefing.
