Mark Klein

Mark Klein
Klein in 2006
Born	(1945-05-02)May 2, 1945 New York City, U.S.
Died	March 8, 2025(2025-03-08) (aged 79) Oakland, California, U.S.
Nationality	American
Known for	Revelations regarding AT&T and the NSA domestic surveillance program Room 641A
Awards	EFF Pioneer Award
Scientific career
Fields	Telecommunications
Institutions	AT&T

National Security Agency surveillance
Map of global NSA data collection as of 2007, with countries subject to the most data collection shown in red
Programs Pre-1978 ECHELON MINARET SHAMROCK PROMIS Since 1978 Upstream collection BLARNEY FAIRVIEW Main Core ThinThread Genoa Since 1990 RAMPART-A Since 1998 Tailored Access Operations Since 2001 OAKSTAR STORMBREW Trailblazer Turbulence Genoa II Total Information Awareness President's Surveillance Program Terrorist Surveillance Program Since 2007 PRISM Dropmire Stateroom Bullrun MYSTIC Databases, tools etc. PINWALE MARINA Main Core MAINWAY TRAFFICTHIEF DISHFIRE XKeyscore ICREACH BOUNDLESSINFORMANT GCHQ collaboration MUSCULAR Tempora
Legislation Safe Streets Act Privacy Act of 1974 FISA ECPA Patriot Act Homeland Security Act Protect America Act of 2007 FISA Amendments Act of 2008
Institutions FISC Senate Intelligence Committee National Security Council
Lawsuits ACLU v. NSA Hepting v. AT&T Jewel v. NSA Clapper v. Amnesty Klayman v. Obama ACLU v. Clapper Wikimedia v. NSA US v. Moalin
Whistleblowers William Binney Thomas Drake Mark Klein Thomas Tamm Russ Tice Edward Snowden
Publication 2005 warrantless surveillance scandal Global surveillance disclosures (2013–present)
Related Cablegate Surveillance of reporters Mail tracking UN diplomatic spying Insider Threat Program Mass surveillance in the United States Mass surveillance in the United Kingdom
Concepts SIGINT Metadata
Collaboration United States CSS CYBERCOM DOJ FBI CIA DHS IAO Five Eyes CSEC GCHQ ASD GCSB Other DGSE BND

Mark Lee Klein (May 2, 1945 – March 8, 2025) was an American AT&T technician and whistleblower who revealed details of the company's cooperation with the United States National Security Agency in installing network hardware at a site known as Room 641A to monitor, capture and process American telecommunications. The subsequent media coverage became a major story in May 2006.