CNN security analysts Frances Townsend and Philip Mudd issued a dire warning about the Islamic State of Iraq and the Levant on Anderson Cooper's AC360.
"You and I talked about this," Cooper said to Mudd, "The State Department officials were telling CNN the Obama administration is less concerned about a potential attack by ISIS in the U.S. than it is about the unknown affiliated actor who decides to do something."
"I think I'd be worried about both," said Mudd, who has worked for the FBI and CIA. "You can't have 100-plus Americans go over who are affiliated with ISIS now. You can't have, I think the Canadians are talking about 100-plus Canadians, 500-plus Brits going over--we're talking about thousands of foreign fighters."
Mudd said the number of fighters affiliated with the terror group that have documents to reenter the United States is "unprecedented."
"Most officials will tell you the estimate of 100 Americans going over is probably a conservative estimate," Townsend said. "It's very hard to track them when they're on false documents."