Every San Francisco neighborhood needs some basic amenities: the corner store, the dog park, the local library branch, and of course the top secret Internet spying facility.

On Monday, the Intercept published an extensive expose on what it alleges is a network of telecommunications facilities secretly eavesdropping on and retaining America’s internet traffic for the National Security Agency [NSA], including one in San Francisco’s SoMa neighborhood, located at 611 Folsom, the austere, windowless building at the corner of Second Street.

The Intercept credits AT&T employees and internal NSA documents for exposing the location of data hubs in New York City, Chicago, and LA, among others.

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But in the case of San Francisco’s own spy shack, the SoMa AT&T facility and its sinister sounding Room 641A were already so well known as to qualify as part of the local color.

According to Intercept reporters Henrik Moltke and Ryan Gallagher, AT&T has been in cahoots with the NSA for years, diverting mind-boggling amounts of user data into the spy agency’s secret repositories:

Atlanta, Chicago, Dallas, Los Angeles, New York City, San Francisco, Seattle, and Washington, D.C. In each of these cities, The Intercept has identified an AT&T facility containing networking equipment that transports large quantities of internet traffic across the United States and the world. A body of evidence—including classified NSA documents, public records, and interviews with several former AT&T employees—indicates that the buildings are central to an NSA spying initiative that has for years monitored billions of emails, phone calls, and online chats passing across U.S. territory.

Allegedly, the NSA particularly prizes its partnership with AT&T thanks to the telecom company’s singular degree of cooperation and the amount of access the company has to private online communications due to its extensive physical network to which other providers often divert traffic.

Note that AT&T and other companies cited in the Intercept story deferred to what they say is a legal obligation to cooperate with intelligence agencies.

While the presence of most of these internet eavesdropping roosts in American cities presumably qualifies as a disconcerting revelation, the AT&T building at 611 Folsom Street was probably one of NSA’s single worst-kept secrets.

In 2006, an AT&T tech named Mark Klein told a court he’d helped set up mechanisms at the SF office for his employers to sweep up data for furtive purposes. The office on Folsom supposedly has an entire room dedicated to NSA activities, known as Room 641A.

The San Francisco based “digital rights group” the Electronic Frontier Foundation [EFF] sued AT&T over its espionage outing in the 2006 case Hepting v. AT&T. An EFF briefing on the suit explains:

AT&T’s internet traffic in San Francisco runs through fiber-optic cables at an AT&T facility located at 611 Folsom Street. Using a device called a “splitter” a complete copy of the internet traffic that AT&T receives – email, web browsing requests, and other electronic communications sent to or from the customers of AT&T’s WorldNet Internet service from people who use another internet service provider – is diverted onto a separate ber-optic cable which is connected to a room, known as the SG-3 room, which is controlled by the NSA. The other copy of the traffic continues onto the internet to its destination.

A federal judge dismissed the case in 2009.

After Klein spilled about the splitting, 611 Folsom became so well known that it has its own Wikipedia page. References to Room 641A even appear in Yelp reviews of the building. (Users gave the alleged spy facility one star.)

Despite this degree of scrutiny, it appears that intelligence agencies still use the Folsom Street office for data collection. But officially, the NSA “can neither confirm nor deny” any alleged uses of the site.