Washington (CNN) Ben Carson on Thursday compared safeguarding Americans from Islamic terrorists who may sneak into the country as refugees to parents protecting their children from rabid dogs.
"If there's a rabid dog running around in your neighborhood, you're probably not going to assume something good about that dog," Carson said during a campaign stop in Alabama. "And you're probably going to put your children out of the way. That doesn't mean that you hate all dogs."
How Republicans would respond to ISIS
He added, "But you're going to put your intellect into motion and you're thinking, 'How do I protect my children at the same time? ... I'm going to call the humane society and hopefully they can come and take this dog away and create a safe environment once again.'"
The Republican front-runner said it would be "foolish" to welcome Syrian refugees without systems in place to thoroughly vet them.
"We have to have in place screening mechanisms that allow us to determine who the mad dogs are. Quite frankly, who are the people who want to come in and hurt us and destroy us," he said.
House passes bill that could limit Syrian refugees
Carson also said that ISIS is more of a threat to America now than Al Qaeda was following the 9/11 attacks.
And he said pulling off the 9/11 attacks "really didn't require a great deal of sophistication."
"You didn't have to be all that great. You had to be able to fly some planes and get a couple people in here. That's going to be a lot more difficult to do now," he said.
Ben Carson: We need to better screen for terrorists before taking Syrian refugees
Carson later praised the House for passing a bill that could limit the intake of Syrian refugees, calling it a positive step.
"The Paris terrorist attacks have demonstrated that terrorists will pose as refugees to enter our land. We must do our utmost to thwart the terrorists' ambitions," Carson said in a statement sent out by his campaign. "The security of the American people, not politics, should be our number one priority. The bipartisan vote in the House today is a very good step in the right direction."