His colleagues were often "astonished to learn we are collecting more in the United States on Americans then we are on Russians in Russia," he said. Many of them were troubled, he said, and several said they did not want to know any more.
"I asked these people, 'What do you think the public would do if this was on the front page?' " he said. He noted that critics have accused him of bypassing internal channels of dissent. "How is that not reporting it? How is that not raising it?" he said.
By last December, Snowden was contacting reporters, although he had not yet passed along any classified information. He continued to give his colleagues the "front-page test," he said, until April.
Asked about those conversations, NSA spokeswoman Vanee Vines sent a prepared statement to The Post: "After extensive investigation, including interviews with his former NSA supervisors and co-workers, we have not found any evidence to support Mr. Snowden's contention that he brought these matters to anyone's attention."
Snowden recounted another set of conversations that he said took place three years earlier, when he was sent by the NSA's Technology Directorate to support operations at a listening post in Japan. As a system administrator, he had full access to security and auditing controls. He said he saw serious flaws with information security.
"I actually recommended they move to two-man control for administrative access back in 2009," he said, first to his supervisor in Japan and then to the directorate's chief of operations in the Pacific. "Sure, a whistleblower could use these things, but so could a spy."
That precaution, which requires a second set of credentials to perform risky operations such as copying files onto a removable drive, has been among the principal security responses to the Snowden affair.