By Jon Mooallem

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."

Over time, during the course of his work, Klein saw company documents and schematics that appeared to reveal that a piece of equipment installed in his internet room, known as a splitter, was making a copy of all the traffic passing through those cables and funneling it downstairs to the secret room. The entire datastream was being duplicated and diverted, Klein later wrote in a memoir: "email browsing, voice-over-internet phone calls, pictures, streaming video, you name it...the communications of millions of people, foreign and domestic, randomly mixed together."

Additional evidence Klein gathered indicated that traffic from more than a dozen other internet providers, whose networks were in communication with AT&T's, was also potentially being copied; that AT&T appeared to have set up similar secret rooms in many other American cities, too; and that his office's secret room housed a processor capable of analyzing the traffic coming from the splitter -- peering inside that intercepted data, not just blindly copying it in bulk.

Klein, who died March 8 in Oakland, Calif., from pancreatic cancer at age 79, told "Frontline": "It dawned on me all at once and I fell out of my chair." Knowing the NSA wasn't lawfully permitted to conduct surveillance domestically, only abroad, Klein concluded he was unwittingly sitting in the middle of, as he put it, "a massive, unconstitutional, illegal operation."

Eventually, he shared what he knew, leading to lawsuits against NSA but little practical effect. The breadth of the agency's mass surveillance programs in the post-9/11 era would be revealed, explosively, by NSA contractor Edward Snowden in 2013. Afterward, Klein told "Democracy Now, " a TV and radio show about public affairs: "Of course I feel very vindicated."

Seven years earlier, Klein had stepped forward as a whistleblower, offering a clear warning -- but with very different results.

'Too scared'

Initially, Klein said nothing about what he'd learned. "I was too scared, " he told "Democracy Now," "and I didn't know if I could find anyone to believe me." Moreover, he couldn't afford to lose his job. Even after taking a buyout from AT&T and retiring at age 59 in 2004, Klein remained wary of government retaliation. He'd taken the documents home with him but debated throwing them out.

In December 2005, the New York Times reported that, after 9/11, President George W. Bush had secretly authorized the NSA to eavesdrop on Americans without warrants as a means of combating terrorism. In the preceding three years, the paper wrote, "the intelligence agency has monitored the international telephone calls and international email messages of hundreds, perhaps thousands, of people inside the U.S.[.]"

Those initial revelations were short on specifics. But Klein figured he was sitting on many of those details himself -- and that the scale and scope of this spying was far greater than reported. Watching the administration defend, mischaracterize and play down the program in response, he resolved to go public. In early 2006, he knocked on the door of the Electronic Frontier Foundation, a digital-rights nonprofit in San Francisco, and asked, "Do you folks care about privacy?"

Using Klein's information, the EFF filed a class-action lawsuit against AT&T, Hepting v. AT&T, setting off a long, overlapping set of legal battles with Klein at their center. The material he had leaked to EFF was put under seal. But they were company documents, not classified government documents. And unlike Snowden, Klein never had a government security clearance and therefore couldn't be prosecuted for violating one.

Instead, the government asked for the case to be dismissed on the grounds that Klein's leak could expose state secrets. A federal judge ruled against that argument. AT&T similarly failed in its bid to compel Klein to return the documents. According to both Cindy Cohn, who worked on the suit for EFF and is now the organization's executive director, and James Brosnahan, one of Klein's personal attorneys, AT&T also threatened to sue Klein, but relented.

Then, in 2008, with the lawsuit building momentum, Congress passed the FISA Amendments Act, instituting changes to the Foreign Intelligence Surveillance Act that simultaneously legalized surveillance programs like the one Klein was exposing and retroactively granted legal immunization to companies like AT&T for their cooperation. The law killed EFF's lawsuit on impact.

A subsequent suit filed against the NSA was thrown out on summary judgment in 2019 and declined to be heard by the Supreme Court three years later. A federal judge ruled that, in the end, Klein "can only speculate about what data were actually processed and by whom in the secure room and how and for what purpose, as he was never involved in its operation" and accepted the government's argument that continuing with the suit posed "a grave risk to the national security."

Klein had spent a week in Washington with Cohn lobbying against Congress's immunity bill. The experience was discouraging. "The level of attention we got in D.C. was sad for all of us," Cohn remembered. Even then-Sen. Barack Obama, who vowed while campaigning for president to support a filibuster on any bill that would give the telecom companies retroactive immunity, voted for the measure.

Cohn notes that some progress has been made in reining in domestic surveillance since then. But Klein didn't seem to take any comfort in those modest, incremental victories. In the end, Cohn said, "He was really, really bitter and angry that nobody listened to him."

During those legal battles, Klein's public profile was initially limited to a few written statements he issued to the press. Eventually, in a handful of television interviews at the time, he presented as a typical, mild-mannered retired engineer, a gentle man with wire-rim glasses, a tidy white mustache and a slightly clipped way of pronouncing "internet" that revealed a vestige of a Brooklyn accent.

"I didn't think of him as particularly radical," Cohn said. "He was somebody who had paid really close attention in civics class and was really committed to the values of this country." Brosnahan called him "a straightforward American workman." Another of his attorneys, Miles Ehrlich, said: "If you had told me he was a conservative Republican, I would have said that makes sense."

Politicized at Cornell

Klein was born on May 2, 1945, in Brooklyn, and grew up a few blocks from Ebbets Field, home of the Brooklyn Dodgers before the team moved to Los Angeles. He was married to Linda Thurston for 40 years before Thurston's sudden death in 2023. "Mark never got over her death," said Martha Robertson, a friend for more than four decades.

In 1962, Klein entered Cornell University to study engineering. But as the U.S. sent troops to Vietnam, he got deeply interested in America's past and present as an imperial power, and graduated with a degree in history instead. "He got pretty politicized," said his older brother, Larry Klein, but "he didn't wear his politics on his sleeve. He was very reserved, a serious student."

At Cornell, Klein joined a protest against the ROTC. He marched in Washington against the war. He traveled to the South to register Black voters and supported the Deacons of Defense and Justice, a group founded by Black World War II veterans that believed in armed self-defense to protect civil-rights activists and Black communities from the Ku Klux Klan.

When he got his first corporate job, as an in-house computer repair technician for Singer Corp., he found it dispiriting and demeaning. "He had to carry a beeper with him so that, even on Saturday and Sundays when he wasn't at work -- even if he was at the movies -- he'd have to leave to fix the goddamn computer," Larry Klein remembered. Robertson recalled that after joining AT&T, Klein was involved in two labor strikes in the 1980s and grew discouraged by a steady "decimation of the workforce and the decimation of the unions."

By the time he found himself working above the Secret Room on Folsom Street in 2003, in fact, Klein had spent more than a decade transferring around the company, dodging downsizing and restructuring as AT&T grappled with the disruptive onset of the internet age. In a 2009 memoir, "Wiring Up the Big Brother Machine...and Fighting It," Klein explained that he and a couple of colleagues had only narrowly managed to survive the closure of another San Francisco office and transfer to Folsom Street. The company, he wrote, "preferred to throw us out with the old equipment."

He seemed to have been driven toward a similarly despondent, even cynical, view of government.

"I didn't trust the government all along," Klein told Media Roots Radio in 2015, "and I never signed on to the Democratic Party as the lesser evil over the Republicans. [Both parties] don't trust the population. They're scared of the population."

Surveillance is "a sign of a government that's detached," he went on. "It's not a people's government. It's a government of the ruling class: a small minority of rich and super rich. And as long as that's the case, they'll continue to spy on everybody." Asked if he had any faith that the American government would ever hold itself to its constitutional ideals, he replied: "None, zero, nada."

Despite all this, Klein didn't blow the whistle out of some contemptuous impulse to bring the government down, but still with some quantum of hope of fixing it. But ultimately, Thornton said, "his experience regarding the AT&T whistleblowing simply was a confirmation of what he knew was true."

Write to Jon Mooallem at jon.mooallem@wsj.com

(END) Dow Jones Newswires

April 11, 2025 10:00 ET (14:00 GMT)

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