LISBON, Portugal — "What do you do when the most powerful institutions in society have become the least accountable to society?"

That was the question Edward Snowden, the former National Security Agency contractor who blew the whistle on numerous global surveillance programs, put to an audience of thousands at the Web Summit technology conference in Lisbon, Portugal on Monday.

"That's the question our generation exists to answer," he added.

Snowden, speaking via video link, said the thing that "chilled" him the most in his discovery of the spying operations was that "intelligence collection and surveillance more broadly was happening in an entirely different way," and was "no longer the targeted surveillance of the past."

In 2013, Snowden's name hit the headlines after the whistleblower leaked classified documents with journalists that detailed surveillance programs run by the NSA that tapped people's cell phone and internet communications.

Washington subsequently charged Snowden with espionage and theft of government property, while his passport was also revoked. He was then granted asylum in Russia, and has lived there ever since.