Edward Loomis worked as an NSA cryptologist from 1964 to 2001. Prior to the 9/11 attacks, Loomis unsuccessfully lobbied the agency to adopt a sophisticated data-collection program -- nicknamed "ThinThread" -- to monitor foreign Internet traffic going through the United States. Loomis told FRONTLINE that had ThinThread been in place before 9/11, the attacks may have been averted.