In Memoriam: Mark Klein, AT&T Whistleblower Who Revealed NSA Mass Spying

EFF is deeply saddened to learn of the passing of Mark Klein, a bona fide hero who risked civil liability and criminal prosecution to help expose a massive spying program that violated the rights of millions of Americans.

Mark didn’t set out to change the world. For 22 years, he was a telecommunications technician for AT&T, most of that in San Francisco. But he always had a strong sense of right and wrong and a commitment to privacy.

Mark not only saw how it works, he had the documents to prove it.

When the New York Times reported in late 2005 that the NSA was engaging in spying inside the U.S., Mark realized that he had witnessed how it was happening. He also realized that the President was not telling Americans the truth about the program. And, though newly retired, he knew that he had to do something. He showed up at EFF’s front door in early 2006 with a simple question: “Do you folks care about privacy?” 

We did. And what Mark told us changed everything. Through his work, Mark had learned that the National Security Agency (NSA) had installed a secret, secure room at AT&T’s central office in San Francisco, called Room 641A. Mark was assigned to connect circuits carrying Internet data to optical “splitters” that sat just outside of the secret NSA room but were hardwired into it. Those splitters—as well as similar ones in cities around the U.S.—made a copy of all data going through those circuits and delivered it into the secret room.

Mark not only saw how it works, he had the documents to prove it. He brought us over a hundred pages of authenticated AT&T schematic diagrams and tables. Mark also shared this information with major media outlets, numerous Congressional staffers, and at least two senators personally. One, Senator Chris Dodd, took the floor of the Senate to acknowledge Mark as the great American hero he was.

We used Mark’s evidence to bring two lawsuits against the NSA spying that he uncovered. The first was Hepting v. AT&T and the second was Jewel v. NSA. Mark also came with us to Washington D.C. to push for an end to the spying and demand accountability for it happening in secret for so many years.  He wrote an account of his experience called Wiring Up the Big Brother Machine . . . And Fighting It.

Mark stood up and told the truth at great personal risk to himself and his family. AT&T threatened to sue him, although it wisely decided not to do so. While we were able to use his evidence to make some change, both EFF and Mark were ultimately let down by Congress and the Courts, which have refused to take the steps necessary to end the mass spying even after Edward Snowden provided even more evidence of it in 2013. 

But Mark certainly inspired all of us at EFF, and he helped inspire and inform hundreds of thousands of ordinary Americans to demand an end to illegal mass surveillance. While we have not yet seen the success in ending the spying that we all have hoped for, his bravery helped to usher numerous reforms so far.

And the fight is not over. The law, called 702, that now authorizes the continued surveillance that Mark first revealed, expires in early 2026. EFF and others will continue to push for continued reforms and, ultimately, for the illegal spying to end entirely.

Mark’s legacy lives on in our continuing fights to reform surveillance and honor the Fourth Amendment’s promise of protecting personal privacy. We are forever grateful to him for having the courage to stand up and will do our best to honor that legacy by continuing the fight.