If you feel nervous about the radical Islamic terror group ISIS, you are not alone.

(Spencer Platt, Getty Images)

A recent CBS/New York Times poll found 60 percent of Americans felt ISIS was a major threat, while 71 percent of respondents said they believed ISIS already had operatives in this country.

Department of Homeland Security experts stress while it's important to be vigilant, people should not become hysterical.

"It's still crucial for all New Jersey residents to keep their eyes open but they don't need to be paranoid, they just need to be aware, they need to not be complacent, they need to keep in the back of their mind there is a threat, people wish to hurt us," said terror and law enforcement expert Randy Sutton.

Sutton said "we can't take on a bunker mentality and load up the house with survival supplies. If we give in to that fear, then we are handing the terrorists their success."

Security expert Vincent Bove agrees that Americans need to be alert but there needs to be a balance.

"Sept. 11 was a wake-up call, and it's also significant the U.S. government is attacking ISIS halfway around the world," he said. "These are dangerous times and all Americans must have an abundance of caution rather than ever being negligent, but there's that healthy balance that allows us to live a happy life of vigilance, blended with not being fearful."

Bove said instead of trying to figure out whether there are any ISIS cells in the U.S. it's better to focus on remaining alert.

"It only takes one lone wolf terrorist or one sympathizer or radical extremist to do us harm," he said. "If we chose the path of vigilance and collaboration with authorities, then we are that much better at protecting the homeland."