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Mark Klein, AT&T Whistleblower Who Exposed NSA’s Mass Surveillance, Dies at 79

Published on: 2025-06-18 08:02:07

Mark Klein, the former AT&T employee who helped expose the fact that the National Security Agency was spying on vast amounts of internet traffic in the U.S. during the mid-2000s, died in Oakland, California, on March 8 at the age of 79, according to the Electronic Frontier Foundation. Klein’s cause of death was pancreatic cancer. Klein was an internet technician for AT&T in San Francisco and had recently retired when he read a New York Times article in late 2005 about mass surveillance of Americans being conducted by the NSA. The article didn’t contain much detail, and Klein went to the EFF in 2006 to help blow the whistle, explaining how NSA used a splitter for all internet traffic flowing through San Francisco, rerouting everything to a room at AT&T called 641A. Klein told PBS Frontline in 2007 about the day in 2002 when the feds came in to build a new room at the AT&T building in San Francisco. The episode, “Spying on the Homefront,” detailed the ways that surveillance of American ... Read full article.