4. Room 641A
Located in the SBC Communications (formerly AT&T) building in San Francisco, Room 641A, has been referred to in recent reports about surveillance activities within the U.S. The Room, which can only be accessed by National Security Agency personnel, is said to collect Internet communications. The data is said to be fed to a massive centralized data center processing facility for analysis. The privacy watchdog group, the Electronic Frontier Foundation, believes it may have been in operation since at least 2001. Up to 20 secret rooms are reportedly believed to be housed at telecommunications facilities in the U.S.