A brutalist fortress in San Francisco serves as a vital artery for the American internet. In 2003, AT&T technician Mark Klein started noticing strange things on the sixth floor of that building. Strange things about Room 641A.
This is a story about the infrastructure we look past, government mass surveillance, and why the machine Mark discovered never actually turned off.
In this Episode
- Mark Klein: An AT&T technician and NSA whistleblower whose sworn declaration exposed the US government's warrantless domestic surveillance program
- Fiber Tapping: The simple physics behind fiber optic splitting and how it's used to duplicate internet traffic without leaving a trace
- Hepting v. AT&T: The class action lawsuit built on Klein's evidence, and how retroactive immunity dismantled it
Episode Music
Archival Audio
Additional Reading
Cohn, C. (2026, April 30). The whistleblower who uncovered the NSA's "big brother machine." The MIT Press Reader. https://thereader.mitpress.mit.edu/the-whistleblower-who-uncovered-the-nsas-big-brother-machine/
Electronic Frontier Foundation. (2014, August 9). How the NSA's domestic spying program works. https://www.eff.org/nsa-spying/how-it-works
FISA Amendments Act of 2008: Congress grants telecommunications companies retroactive immunity from civil suits for complying with NSA terrorist surveillance program. (2009). Harvard Law Review, 122(4), 1271–1278. https://harvardlawreview.org/print/vol-122/congress-grants-telecommunications-companies-retroactive-immunity-from-civil-suits-for-complying-with-nsa-terrorist-surveillance-program-ae-fisa-amendments-act-of-2008-pub-l-no-110-261/
Harris, B. (2025, June 12). What is inside Room 641A. Covert Access Team. https://covertaccessteam.substack.com/p/what-is-inside-room-641a
Klein, M. (2007). Public unredacted Klein declaration [Legal declaration]. Electronic Frontier Foundation. https://www.eff.org/document/public-unredacted-klein-declaration
Klein, M. (2009). Wiring up the big brother machine... and fighting it. BookSurge Publishing. (Bookshop.org affiliate link)
Marcus, J. S. (2006). Declaration of J. Scott Marcus in support of plaintiffs' motion for preliminary injunction [Court filing]. Hepting v. AT&T Corp., No. C-06-0672-JCS (N.D. Cal.). Electronic Frontier Foundation. http://www.eff.org/legal/cases/att/SER_marcus_decl.pdf
McDaniel, E. (2026, June 12). A key U.S. spy tool has lapsed — now what? NPR. https://www.npr.org/2026/06/12/nx-s1-5856291/fisa-702-surveillance-expiration-bill-pulte
New, W. (2003, September 25). Congress funds Defense, kills Terrorism Information Awareness. Government Executive. https://www.govexec.com/defense/2003/09/congress-funds-defense-kills-terrorism-information-awareness/15051/
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