“He was not a collector,” he said. “I don’t know he could do anything like that,” adding that Snowden, a low-ranking contractor, would not have the authority or access to listen in on phone calls or read emails from anyone…

“A rogue collector would lose his clearance and be run out of the organization,” said Joel Brenner, a former inspector general and senior counsel for the NSA who left the agency in 2010. Brenner said that he didn’t recall ever dealing with “rogue collecting” during his time at as inspector general.

What did occupy his time, said Brenner, was what he called errors and “over-collection”— information with no foreign intelligence value or unintentionally collected information about a U.S. person. “You’ve got to understand that over-collection is to some degree inevitable,” he said. “When you are taking information off of a fiber optic cable with unimaginably large volumes passing at the speed of light, you are going to get some stuff that has to be filtered out later.”

Another issue, Brenner said, is “analytical error,” when a collector who believes he or she was targeting a foreign person turned out to instead be targeting an American citizen. In such an instance, the NSA is compelled to eliminate the data that was collected. “If someone is making lots of errors they will get a talking-to.”