The latest revelations by the Guardian about the NSA spying program
US officials vehemently denied this specific claim. Mike Rogers, the Republican chairman of the House intelligence committee, said of Snowden's assertion: "He's lying. It's impossible for him to do what he was saying he could do."
But training materials for XKeyscore detail how analysts can use it and other systems to mine enormous agency databases by filling in a simple on-screen form giving only a broad justification for the search. The request is not reviewed by a court or any NSA personnel before it is processed.
I'm shocked (shocked!) that the government was lying and not Snowden.