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Distribution and use of this material are governed by our Subscriber Agreement and by copyright law. For non-personal use or to order multiple copies, please contact Dow Jones Reprints at 1-800-843-0008 or visit www.djreprints.com. https://www.wsj.com/us-news/mark-klein-whistleblower-dies-73f434c7 1. U.S. Mark Klein, a Whistleblower Who Revealed Domestic Spying, Dies at 79 The AT&T technician predated Edward Snowden by seven years, but his allegations were never able to achieve traction By Jon Mooallem Share Resize --------------------------------------------------------------------- Listen (3 min) Headshot of Mark Klein, the whistleblower who revealed the NSA wiretapping story.Mark Klein, shown in 2007, said he was initially scared to come forward. Photo: Marvin Joseph/The Washington Post/ Getty Images In October 2003, the AT&T technician Mark Klein was transferred to a small office on San Francisco's Folsom Street where he was tasked with maintaining the seventh floor "internet room," where fiber-optic cables carried billions of bits of data across the company's network every second. Klein had worked at AT&T since 1981, first in New York, then in various offices around the Bay Area. Klein and his colleagues were all aware of the mysterious room--Room 641A--that had recently been constructed by people from the National Security Agency, directly below Klein's internet room, but they weren't given an inkling of its purpose. Only one or two AT&T employees with NSA clearance could enter. Everyone called it "the secret room." Copyright (c)2025 Dow Jones & Company, Inc. 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All Rights Reserved. Copyright (c)2025 Dow Jones & Company, Inc. All Rights Reserved This copy is for your personal, non-commercial use only. Distribution and use of this material are governed by our Subscriber Agreement and by copyright law. For non-personal use or to order multiple copies, please contact Dow Jones Reprints at 1-800-843-0008 or visit www.djreprints.com.