U.S. officials issued a somber warning today that the coming holiday season could mean "opportunities for violent extremists" to strike, especially as terror groups are squeezed abroad.
"Though we know of no intelligence that is both specific and credible at this time of a plot by terrorist organizations to attack the homeland, the reality is terrorist-inspired individuals have conducted, or attempted to conduct, attacks in the United States," reads a bulletin posted online today by the Department of Homeland Security.
The warning said terrorists could attempt to target "public events and places where people congregate."
The bulletin came days after an ISIS magazine called on the terrorist group's followers to use vehicles to attack popular outdoor attractions, like a New York parade.
"It is very difficult to protect events like large gatherings such as parades from these types of attacks using vehicles, and we saw that last summer in Nice," said Matt Olsen, former director of the National Counterterrorism Center and current ABC News consultant.
In July a man driving a large truck barreled into a packed crowd near the waterfront in Nice, France, killing more than 80 people before he was gunned down by police. ISIS later claimed the man was one of their "soldiers," though the ISIS statement suggested the group did not have foreknowledge of the plot.
While a senior law enforcement official reiterated that there's no specific or credible threat at this time, the official said New York City's counter-terrorism apparatus, from the NYPD to the FBI and other agencies, are ramping up special protocols used for major events.
John Miller, NYPD Deputy Commissioner for Intelligence and Counterterrorism, said Monday said his organization has specifically prepared for vehicle-borne attacks since the tragedy in France.
"The intelligence bureau identified 181 locations that rent trucks to the public in the metropolitan area. Of that we went to 135 of those locations that rent vehicles under 26,000 pounds, where you wouldn't require the possession of a commercial driver's license to operate that. Our Incident Prevention Unit provided them with very useful guidance on how to identify suspicious behavior and characteristics among people who are potential renters of those vehicles," Miller told reporters.
But Miller said he saw ISIS's "threat" more as "psychological warfare."
"What you see is the psychological warfare of printing materials that indicate to be afraid, be very afraid. We never cede to that," he said. "On the other hand, we have seen instances where [ISIS] has put out the call and people have risen to that call, which is why we have one of the most robust, complicated counter-terrorism programs in the world, and why we invest so many resources into it."
A counter-terrorism official said that an ISIS-inspired attacker is of particular concern because the group may seek to "distract" the world from its battlefield loses in Iraq and Syria.
"As [ISIS] sheds its remaining safe havens, the group's pretensions of a 'caliphate' look increasingly bankrupt and desperation will likely fuel its pleas for action," the official said.