Edward Snowden has very sensitive "blueprints" detailing how the National Security Agency operates that would allow someone who read them to evade or even duplicate NSA surveillance, a journalist close to the intelligence leaker said Sunday.

Glenn Greenwald, a columnist with The Guardian newspaper who closely communicates with Snowden and first reported on his intelligence leaks, told The Associated Press that the former NSA systems analyst has "literally thousands of documents" that constitute "basically the instruction manual for how the NSA is built."