James Martin/CNET

SAN FRANCISCO -- It was a walk down memory lane for Mark Klein on Tuesday night, when a crowd gathered to hear him speak out, yet again, about the secret sharing of data between a top communications company and the US government.

Klein, a retired AT&T technician, leaked several internal AT&T documents in 2006 that showed that the NSA was collecting data from AT&T through a restricted room, 641A.

"I was wiring the Big Brother machine, which pissed me off," he said, standing outside of the AT&T building that he said houses 641A. Roughly 200 people gathered on the corner of the downtown San Francisco intersection to hear Klein speak as a part of "The Day We Fight Back," a campaign against mass surveillance from the government. Throughout the day, Internet activists placed nearly 80,000 calls and sent nearly 160,000 e-mails to their representatives in Congress to protest the NSA's tactics.

For AT&T's part, the company maintains that the company does "not allow any government agency to connect directly to our network" to gather customer information.

As protesters chanted and sang along to an "Every Breath You Take" video projected onto the side of the AT&T building, a handful of police watched from the edges of the building's entrance. But the crowd was quiet as Klein spoke, save a few boos when Sen. Dianne Feinstein's name or the NSA bill she is sponsoring was mentioned, and applause for Klein. He called Feinstien's bill "just an insult."

"I'll tell you what will be real reform," he said. "Rip out those secret rooms. Rip out the rooms throughout the country."

Only NSA-approved workers were allowed in the room, Klein said, but he had the AT&T schematics that proved there were splitters installed inside the room that allowed data from AT&T's lines to be copied for the NSA.

"I should take those documents with me," he said he thought when he retired in 2004. "Maybe I can show them to someone."

In 2006, he gave them to the Electronic Frontier Foundation, which then used the documents in a suit alleging that AT&T violated federal wiretapping laws by cooperating with the NSA. While Klein's story may sound similar to how NSA whistleblower Edward Snowden leaked documents about the NSA's spying practices, Klein said his actions didn't cause as much of a stir since his documents were AT&T documents and not the government's. The matter eventually disappeared in the news cycle.

"This quieted down a couple of years and then along came Ed Snowden...Ed Snowden had NSA documents and they couldn't ignore them," he said.