In late 2003, the Bush administration reversed a long-standing policy requiring agents to destroy their files on innocent American citizens, companies and residents when investigations closed.

On average, since 9/11, the FBI reckons that just over 100,000 terrorism leads each year have come over the transom. Analysts and agents designate them as immediate, priority or routine, but the bureau says every one is covered.

A national security letter cannot be used to authorize eavesdropping or to read the contents of e-mail. But it does permit investigators to trace revealing paths through the private affairs of a modern digital citizen.

Barton Gellman Quotes