Will latest ISIS strikes inspire attack on U.S.?

While U.S. intelligence has not identified a specific threat from ISIS to the homeland, sources say there are new worries that the militant group could inspire retaliatory attacks in response to the American strikes in Syria, CBS News correspondent Bob Orr reports.

One fear is that a lone wolf, who may not be on law enforcement's radar, could be motivated to act in the name of ISIS. That kind of threat is very difficult to detect.

The other worry is about those Americans and Western Europeans who have already joined the ISIS ranks -- the FBI is trying to track more than 100 Americans who have gone, or have tried to go to Syria. Some have been stopped and arrested. Others are under surveillance. The concern is there may be some radicalized Americans who have returned from the fight without our knowledge.

At least three Americans have been killed fighting with militant groups including ISIS. Others remain on the battlefield.

The larger threat against the U.S. may be the al Qaeda-affiliated group known as Khorasan, which the U.S. targeted separately from ISIS, citing "imminent threat plotting."

CBS News' senior security contributor and former CIA Deputy Director Mike Morell spoke about the significance of the attack against Khorasan.

"I think it's important that the fight against ISIS has now gone to Syria. But I think it's even more important that we struck the Khorasan group last night," CBS News' senior security contributor and former CIA Deputy Director Mike Morell said.

The U.S. central command's press release referencing the "imminent threat plotting" suggests to Morell that "we had detailed intelligence on attack plotting, either in the United States, or in Western Europe, or in both. So these eight strikes in Northwestern Syria, a long way from the ISIS targets were, very, very important."

Meanwhile, ISIS continues to mount a very aggressive social media campaign, aimed at recruiting more young radicals. The terror group is now posting web videos with ISIS logos over popular video games like "Grand Theft Auto."

Westerners are increasingly appearing in ISIS propaganda videos. A new tape, titled "Flames of Wars" features a masked man who speaks in clear unaccented English.

The FBI believes the speaker is either American or Canadian and the U.S. government is now trying to identify that man and his associates.