Wired has the evidence gathered by the AT&T whistleblower. Go read:

In San Francisco the “secret room” is Room 641A at 611 Folsom Street, the site of a large SBC phone building, three floors of which are occupied by AT&T. High-speed fiber-optic circuits come in on the 8th floor and run down to the 7th floor where they connect to routers for AT&T’s WorldNet service, part of the latter’s vital “Common Backbone.” In order to snoop on these circuits, a special cabinet was installed and cabled to the “secret room” on the 6th floor to monitor the information going through the circuits. (The location code of the cabinet is 070177.04, which denotes the 7th floor, aisle 177 and bay 04.) The “secret room” itself is roughly 24-by-48 feet, containing perhaps a dozen cabinets including such equipment as Sun servers and two Juniper routers, plus an industrial-size air conditioner.

The normal work force of unionized technicians in the office are forbidden to enter the “secret room,” which has a special combination lock on the main door. The telltale sign of an illicit government spy operation is the fact that only people with security clearance from the National Security Agency can enter this room. In practice this has meant that only one management-level technician works in there. Ironically, the one who set up the room was laid off in late 2003 in one of the company’s endless “downsizings,” but he was quickly replaced by another.

And in other NSA news, Josh says he thinks Verizon is basically lying. Go read why.