Sean Joyce, Deputy Director of the Federal Bureau of Investigation, detailed certain terrorist plots stopped because of the controversial NSA program that collects private data from American citizens. 

One such plot Joyce recounted dates back to the fall of 2009 when the agency intercepted an email from an individual in Pakistan to an individual inside the U.S. about perfecting the recipe for explosives.

The American in question was located in Denver, Colorado, and he was then followed by authorities to New York. His name is Najibullah Zazi - the man arrested after Joyce said bomb-making components were found in backpacks in his possession.

Zazi later confessed to a plot to bomb the New York subway system with backpacks.

Hear Joyce's detailed account of the intel used to stop the plot.