The National Security Agency and Justice Department mounted a vigorous defense of the government's controversial surveillance efforts on Tuesday, with NSA chief Gen. Keith Alexander claiming they have helped prevent "potential terrorist events" over 50 times since 9/11.
Officials insisted the programs protect Americans from unwarranted intrusion, as they began to shed light on the scope of the secretive effort in a rare public hearing.
Disclosing new details, a top FBI official claimed the surveillance efforts helped disrupt a plot to bomb the New York Stock Exchange.
