When the National Security Agency's most secretive programs were first leaked in June by the former contractor Edward Snowden, the Agency was the target of countless reports and at the center of an unprecedented international response. No other U.S. agency had experienced any-thing nearing this level of criticism in recent times. As we constructed it, the N.S.A. was a story about a debate, not a villain, and we added to that debate with important information. We wanted to provide clarity on the technical capabilities of the NSA and to do that we knew we needed to get inside the Agency to see how it operates.