Klein, a former AT&T technician turned whistleblower, exposed mass surveillance by the U.S. government in 2006.

Mark Klein, the former AT&T employee who helped expose the fact that the National Security Agency was spying on vast amounts of internet traffic in the U.S. during the mid-2000s, has died, according ...

The Electronic Frontier Foundation (EFF) recently announced the passing of Mark Klein, the AT&T whistleblower who exposed the ...

In 2006, he shared corporate documents showing how the National Security Agency was accessing internet data through a secret room in an AT&T office building.