NSA to '60 Minutes': Snowden Gave World 'Roadmap' to Protect Info

Of all the secrets stolen by Edward Snowden – and there were almost 2 million – the most worrisome are the gaps in intelligence on other countries, NSA employees told "60 Minutes."

With much of the public sentiment turning against the agency over charges that Americans' personal conversations are being monitored, the National Security Agency gave "60 Minutes" access to areas and personnel not normally granted.

Rick Ledgett, who heads the team looking into the Snowden leaks, said the former NSA contract employee did a scraping of information rather than picking and choosing. The information of America's gaps in intel could let other countries know what to do to stay a step ahead of the United States.

"It would give them a roadmap of what we know, what we don't know, and give them, implicitly, a way to protect their information from the U.S. intelligence community's view," Ledgett told "60 Minutes."

Those documents have not been leaked, but Snowden still holds a million and a half unreleased secret files. He is holed up in Russia on temporary asylum after initially fleeing to Hong Kong. He has said that others have access to the documents and can release them if anything happens to him, though he has denied that he was making a "doomsday" threat.

Ledgett said it would be worth talking to Snowden about amnesty if he would return to the United States and stop the leaking.

"I would need assurances that the remainder of the data could be secured, and my bar for those assurances would be very high," he said. "It would be more than just an assertion on his part."

But that's not a universal opinion in the agency, and Ledgett's boss, NSA Director Gen. Keith Alexander is among those who don't agree.

"This is analogous to a hostage taker taking 50 people hostage, shooting 10 and then saying, 'If you give me full amnesty I'll let the other 40 go,'" Alexander said. "I think people have to be held accountable for their actions."

Alexander said he offered to resign over the scandal since it happened on his watch. Secretary of Defense Chuck Hagel and Director of National Intelligence James Clapper told him he needed to stay.

The NSA also talked to "60 Minutes" about its efforts to prevent cyber attacks that could cripple the U.S. economy. The recent discovery of the BIOS plot was aimed to do just that. The NSA would not tell "60 Minutes" which nation was behind the plot, but cyber security experts briefed on it said it was China.

NSA director of cyber security Debora Plunkett told "60 Minutes" that such an attack could take down the entire U.S. economy.

"There are absolutely nation states who have the capability and the intentions to do just that," Plunkett said.