Room 641A: the sworn declaration that proved the NSA copied America’s internet traffic

Mark Klein worked as an AT&T technician for more than two decades. In 2003, during routine upgrade work at AT&T’s central office at 611 Folsom Street in San Francisco, he documented the construction of a secure room on the sixth floor, accessible only to personnel with NSA clearance, with no door handle on the inside. He retained internal AT&T documents describing the installation: network diagrams, a cabling schedule identifying which circuits were connected, and equipment lists.

The equipment included fiber-optic splitters that copied the entire signal passing through AT&T’s WorldNet internet backbone, at the time carrying a substantial share of US internet traffic, and Narus STA 6400 devices, semantic traffic analyzers capable of deep packet inspection at backbone speed. The splitters did not distinguish domestic from international traffic and did not select for specific targets. They copied everything passing through the affected circuits.

Klein waited until his retirement to disclose what he had documented, then provided his materials to the Electronic Frontier Foundation, which used them as the basis for Hepting v. AT&T, filed in 2006. His declaration was filed with the US District Court for the Northern District of California on April 8, 2006. Unlike an anonymous leak, Klein put his name, his professional history, and his willingness to be cross-examined behind the disclosure.

Congress responded to the surveillance revelations Klein’s evidence helped expose by granting telecommunications companies retroactive legal immunity for cooperating with the program, effectively ending Hepting v. AT&T. A related case, Jewel v. NSA, in which Klein also provided a declaration, was ultimately dismissed by the courts on the grounds that plaintiffs could not prove the surveillance had caused them specific, individualized harm, a standard the government argued could not be met without revealing state secrets. In April 2019, the Northern District of California went further, ruling that Klein could not establish the content, function, or purpose of the room based on his own independent knowledge, since he was never involved in its operation.

Klein’s technical documentation was never successfully rebutted. What the courts found insufficient was proving individual harm from a program the government would not confirm operational details of, a different question than whether the room and its equipment existed as Klein described.

This establishes that a named, credentialed AT&T technician provided sworn testimony, internal company documents, and technical schematics describing equipment installed specifically to copy internet traffic in bulk and route it to the NSA, filed as court exhibits and never technically discredited. Subsequent disclosures, including material from Edward Snowden in 2013, described a program called FAIRVIEW involving AT&T cooperation with the NSA across multiple US cities, consistent with Klein’s account.

What this does not establish, per the courts’ own rulings, is the specific legal authority under which the program operated, the exact scope of what was retained versus discarded, or individualized proof that any specific person’s communications were read by a human analyst rather than processed and discarded by automated systems. Those questions were left legally unresolved, not because Klein’s technical account was disproven, but because the courts found the broader claims unprovable without the government confirming classified operational details it declined to confirm.