The information Mark gave us made the whispers we had heard over the years from our friends at telecommunication companies make more sense. By his account, mass spying involved the internet’s deepest layer, known as the “backbone.” A set of large providers — big companies, academic institutions, and governments — operate a series of powerful computers that provide the backbone’s main data routes.
AT&T operated part of the internet backbone from the Folsom Street facility. One component of Mark’s job was to maintain the section of the AT&T system that routed traffic from AT&T’s internal networks to the internet backbone via a set of connections called “peering links.” What Mark was telling us, and what his documents were showing, was that the NSA was now tapping in at these junctures.
Mark had been a technician at AT&T for many years. In mid-2003, he was transferred to the Folsom Street building and charged with maintaining the room where AT&T’s own fiber-optic network connected to the rest of the internet.
Mark told us that the fiber-optic cables carrying traffic to and from AT&T’s portion of the backbone converged on the seventh floor of the Folsom Street building. This was reasonable. But he showed us that those cables also connected down to the sixth floor of the building. The sixth floor was where the weirdness happened. Sometime in 2002, a “secret room” (designated 641A) had been built on that level of the building, accessible only to workers with NSA clearances. Mark didn’t have clearance himself, but he knew and worked with the person who did and had access to that room.