CHICAGO (CBS) — A new terror warning in United States raises concerns for more than a hundred terror investigators working out of Chicago’s West Side FBI headquarters.

CBS 2 Chief Correspondent Jay Levine reports there is concern and admission that Chicago could be a target of an attack, and a target for terrorist recruiters.

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“In the history of terrorism, Chicago has always been a target,” said FBI agent Robert Holley.

Holley pointed to the terrorist publication Inspire’s repeated references to Chicago, the recent tweet that ISIS was already here, explosives-packed printers shipped to Chicago addresses and the deadly terrorist attack in Mumbai, planned by Chicagoan David Headly.

“There are individuals here that are not only ISIS but some of these other terrorist groups,” he said.

Like Khorasan, whose bases the U.S. and allies hit Monday night. Their plans and those revealed in Australia last week could be signs that the ISIS terror campaign is spreading.

We are also seeing a sophisticated internet video propaganda war; the popular American video game Grand Theft Auto modified to send a message and what appear to be Americans in their new video Flames of War.

They also use social media to recruit.

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“I think what should surprise us is their sophistication. Uh but what the better question is is how are we going to counter them and how are we going to react to them. What happens when these individuals who are potentially fighting overseas decide to come back here,” said Michael Masters with Cook County Homeland Security.

But a Chicago lawyer and Loyola professor with close ties to the Muslim community says be vigilant, but don’t overreact.

“What I would be fearful of creating new law out of reaction to beheading of two American journalists. That’s not to say that’s not an outrage, but to overreact is to play in to hands of ISIS,” said Professor Thomas Durkin.

Bridgeview Mosque Foundation President Oussama Jammall says they are trying to prevent people who could be targeting the mosque and their children.

“We will continue to educate our young people and clarify for them the misconceptions that ISIS and like-minded of ISIS trying to promote, trying convince others,” Jammall said.

“If it gets to that point where the rhetoric is problematic, our imams will report that person to the necessary law enforcement,” said Ahmed Rehab of the Council of American-Islamic Relations. “It has happened and they have reported such individuals.”

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Tuesday’s knife attack in Australia and warnings of lone wolf attacks here, are indications that terrorists are once again targeting the West. While the FBI’s got a lot on its plate, political corruption, white collar crime, and increasingly inner city violence, terrorism FBI Chief Holley says, is a top priority.