“That’s one of the downsides of U.S. involvement,” former deputy CIA director Michael Morrell told CBS News in June. “The more we visibly get involved in helping the [Iraqi] government fight these guys, the more we become a target.”

A U.S. intelligence official would not say whether the threat level has escalated, saying the U.S. continues to monitor the known ISIS threat. “ISIS has previously stated its willingness to strike targets outside of the region and the [intelligence community] is working in close coordination with our allies to track these threats,” says Brian Hale, spokesman for the Director of National Intelligence.

In July, Brett McGurk, the top State Department official for Iraq, told the Senate Foreign Relations Committee that the 30 to 50 suicide bombers per month deployed in Syria and Iraq by ISIS “are increasingly western passport holders,” and that “it is a matter of time before these suicide bombers are directed elsewhere.”