The National Security Agency has revealed some 31,000 documents detailing specific gaps in the agency's spying operations in countries like China, Russia and Iran are in the hands of former contractor Edward Snowden.
The documents were described as the "keys to the kingdom" by a senior NSA staffer Rick Ledgett who is leading a task force investigating the torrent of Snowden leaks.
"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 US intelligence community's view," Ledgett told the US 60 Minutes program.
NSA chief General Keith Alexander defended the agency spy operations indicating it could have prevented 9/11 if it had the interception capabilities then that it holds today.
What Gen. Alexander is talking about is that two of the 9/11 hijackers, Khalid al-Mihdhar and Nawaf al-Hazmi were in touch with an al Qaeda safe house in Yemen. The NSA did not know their calls were coming from California, as they would today.
"I think this was the factor that allowed [hijacker Khalid al-Mihdhar] to safely conduct his plot from California. We have all the other indicators but no way of understanding that he was in California while others were in Florida and other places," Gen. Alexander said.
The four star general argued the agency did not infringe the privacy of Americans and was currently eavesdropping on phone calls for about 60 suspected US citizens globally.
However the interview did not canvass whether the agency had created backdoors in security mechanisms such as the Dual EC_DRNG algorithm.
Ledgett indicated Snowden may have stolen 1.7 million secret NSA documents.
He said the agency spent "tens of millions" of dollars replacing machines that Snowden had access to, including any cables he used when stealing the documents.
The 25-year NSA veteran also added Snowden got access to documents to cheat his way through an agency examination.
Cyber defence head Debora Plunkett said the agency foiled an attack against US targets that attempted to brick BIOS systems. Agency sources said the attacks were launched by China.
The attack involved malware distributed through an update that would render machines unusable.
It was one attack that the agency was able to foil but Plunkett said nations had the resources to conduct major attacks against critical infrastructure.
"Don't be fooled. There are absolutely nation states who have the capability and the intentions to do just that," Plunkett said.
She said the US Government lacked the capabilities to detect and prevent such attacks.