With the world's most hunted terrorist dead, the U.S. is on high alert hoping another attack doesn't happen, but could you spot a terrorist if one were living next door to you?
We all better learn how to spot 'em because the experts agree, the best way to combat terrorism is through the eyes and ears of the American public.
At some of our busiest airports, security agents are studying travelers' behavior.
Highly trained agents, can use something called the facial action coding system or "facs" that can read a person's most subtle micro-expressions to tell if they're lying.
High tech surveillance cameras can even be programmed to identify someone whose facial expressions are different from others in line but those tools aren't available to us.
Dr. Gregory Moore, director of the University of Notre Dame's Center for Intelligence Studies says all of us should learn how to spot a terrorist. How do you distinguish a tourist taking pictures and a terrorist surveying a target? Are they taking pictures of the scenery, or of a high security facility?
Someone spending too much time looking at a public building, taking notes, copying blueprints, timing response times, and stealing uniforms so they can gain access.
"It really boils down to this, if you see something, then say something," said Moore. "It's not a perfect process, but asking the American public to be the eyes and ears to help combat terrorism may our most effective weapon."
Of course there will likely be many false alarms but as Dr. Moore points out, "but what if you're right, what if you're right?"
For more information on how to spot a terrorist click on the links to the right.