NPR Fresh Air: In 2013, Edward Snowden was an IT systems expert working under contract for the National Security Agency when he traveled to Hong Kong to provide three journalists with thousands of top-secret documents about U.S. intelligence agencies' surveillance of American citizens.

To Snowden, the classified information he shared with the journalists exposed privacy abuses by government intelligence agencies. He saw himself as a whistleblower. But the U.S. government considered him a traitor in violation of the Espionage Act.

After meeting with the journalists, Snowden intended to leave Hong Kong and travel — via Russia — to Ecuador, where he would seek asylum. But when his plane landed at Moscow's Sheremetyevo International Airport, things didn't go according to plan.

"What I wasn't expecting was that the United States government itself ... would cancel my passport," he says.

Snowden was directed to a room where Russian intelligence agents offered to assist him — in return for access to any secrets he harbored. Snowden says he refused.

"I didn't cooperate with the Russian intelligence services — I haven't and I won't," he says. "I destroyed my access to the archive. ... I had no material with me before I left Hong Kong, because I knew I was going to have to go through this complex multi-jurisdictional route."

Snowden spent 40 days in the Moscow airport, trying to negotiate asylum in various countries. After being denied asylum by 27 nations, he settled in Russia, where he remains today.

"People look at me now and they think I'm this crazy guy, I'm this extremist or whatever. Some people have a misconception that [I] set out to burn down the NSA," he says. "But that's not what this was about. In many ways, 2013 wasn't about surveillance at all. What it was about was a violation of the Constitution."

Snowden's 2013 revelations led to changes in the laws and standards governing American intelligence agencies and the practices of U.S. technology companies, which now encrypt much of their Web traffic for security. He reflects on his life and his experience in the intelligence community in the memoir Permanent Record.

On Sept. 17, the U.S. Justice Department filed suit to recover all proceeds from the book, alleging that Snowden violated nondisclosure agreements by not letting the government review the manuscript before publication; Snowden's attorney, Ben Wizner, said in a statement that the book contains no government secrets that have not been previously published by respected news organizations, and that the government's prepublication review system is under court challenge.