"Next step for body scanners could be trains, boats, metro"

"The next step in tightened security could be on U.S. public transportation, trains and boats.

Homeland Security Secretary Janet Napolitano says terrorists will continue to look for U.S. vulnerabilities, making tighter security standards necessary.

“[Terrorists] are going to continue to probe the system and try to find a way through,” Napolitano said in an interview that aired Monday night on "Charlie Rose.""