In its more than 60-year history, the NSA has gathered intelligence used in a broad span of government efforts from keeping the Suez Canal open to trade following Egyptian nationalization in the '50s to intercepting key communications from Russian ships during the Cuban missile crisis. In the latter incident, the CIA discovered that the Soviet Union was preparing to install nuclear warheads in Cuba. NSA SIGINT later showed that the stakes had been raised when agents learned through cryptology work that the Russians had taken over control of Cuban air defense controls. NSA-gained intelligence stemmed fears of an all-out nuclear war by showing that Soviet leaders had decided not to challenge a naval quarantine implemented by U.S. forces at Cuban ports [sources: NSA,NSA].
Before and during Operation Desert Storm in 1991, the NSA SIGINT provided intelligence to the U.S. and its allies, as well as secure communications on the battlefield. After the events of 9/11, the NSA came under fire for failing to catch the plot to attack the World Trade Center. The NSA countered that it had intercepted two messages that something major was going to happen on Sept. 11 but there was no information in them on where or what the action would be [sources: NSA, NSA]. At the time too, the NSA was focused on foreign surveillance rather than domestic surveillance. The NSA was also criticized for failing to keep up with the technological advances needed to counter terrorism [source: NOVA].
Since then, the NSA has worked hard to improve its technological capabilities, as the people that the agency keeps its eye on have changed in many ways. No longer are adversaries likely to be wearing a uniform or otherwise readily identifiable. Instead, persons of interest are often those operating in small cells communicating by cell phone and Internet. There is also the dreaded "lone wolf" working virtually on his or her own, like Faizal Shahzad, who was arrested for attempting to bomb Times Square in 2010 [source: Martin].
The events of Sept. 11, 2001 also changed who the target of NSA surveillance would be – it was no longer just people living outside the U.S.