AT&T installed specialized surveillance equipment in its digital switching centers to allow the National Security Agency to conduct surveillance on telephone calls and Internet traffic, according to a former AT&T employee.

On January 31, the Electronic Frontier Foundation filed a lawsuit against AT&T alleging that the company cooperated with the NSA in violation of law and spied on the communications of innocent Americans.

This week, Mark Klein, a retired AT&T technician, submitted an affidavit in the case, stating that he was involved in the installation of the surveillance and data mining equipment that NSA used to implement the terrorist surveillance program that President George W. Bush authorized by secret executive order in October 2001.

According to a statement (PDF) released by Klein’s attorney, an NSA agent showed up at the San Francisco switching center in 2002 to interview a management-level technician for a special job. In January 2003, Klein observed a new room being built adjacent to the room housing AT&T’s #4ESS switching equipment, which is responsible for routing long distance and international calls. . . .

AT&T was also diverting traffic routed from its network to or from other domestic and international providers, according to Klein’s statement.

The secret room also included data-mining equipment called a Narus STA 6400, “known to be used particularly by government intelligence agencies because of its ability to sift through large amounts of data looking for preprogrammed targets,” according to Klein’s statement. — Wired News (Props.)

The equipment being used is capable of processing hundreds of thousands of phone calls and/or Internet connections in real time, sifting through the data for items of interest and forwarding those onward to NSA.

President Bush has defended the terrorist surveillance program as fully legal, despite the 1978 Foreign Intelligence Surveillance Act which apparently prohibits this sort of surveillance. The program has also been criticized as ineffective, finding only thousands of innocent Americans, despite protestations to the contrary by the administration. Intelligence gained through the program is routinely shared with other government agencies.

Attorney General Alberto Gonzales testified before Congress on Thursday that it was possible for the government to conduct surveillance on purely domestic communications without any sort of warrant.