WHITE PLAINS, N.Y. — The terror attack that left eight dead in Manhattan on Tuesday could be a frightening indication of things to come in the war on terror in the U.S., experts cautioned.

The simplicity of planning and carrying out similar attacks, in which a man drove a pick-up truck onto a bike path near the World Trade Center and plowed into cyclists, makes them difficult to guard against and prevent.

Authorities stand near a damaged Home Depot truck after a motorist drove onto a bike path near the World Trade Center memorial, striking and killing several people on Oct. 31, 2017, in New York.

“It’s now, unfortunately, becoming almost conventional, because it’s so easy," said Charles Strozier, director of the Center on Terrorism at John Jay College of Criminal Justice. "This particular form of attack has not reached anywhere in the United States before. We’re vulnerable. Democratic societies are open and they can be penetrated.”

But while a relatively new phenomena on U.S. soil, Tuesday's New York City attack mirrors several terror incidents over the past year in Barcelona, London, Germany and Nice.

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"These sorts of things are brewing in basements around the country right now," said John Shane, a professor of law and police science at John Jay. "It's the quintessential stranger-to-stranger crime that we in policing circles and research circles have talked about for decades.

“When you hear of a street robbery or you hear of a murder taking place, the one that scares you the most is the one that happens seemingly at random," Shane said. "And that’s exactly what these incidents do. They're exceptionally difficult to guard against.”

Bruce Hoffman of the Wilson Center in Washington, D.C., said the Big Apple remains a prime target for terrorists more than 16 years after the Sept. 11, 2001, attacks. 

He said New York is certainly part of the Islamic State’s strategy for three years now, a strategy that still exists despite ISIL’s military defeats.

“New York is a hardened target,” Hoffman said. “If they can pierce New York’s defenses, it sends a very strong psychological blow by terrorists.

“This is the kind of incident terrorist organizations see as reversing any setbacks they may have taken,” he added. “It immediately instills fear and anxiety, the stock and trade of terrorists.”

This kind of attack he sees as not random, but designed to disrupt big community events, such as New York’s Halloween Parade set for Tuesday night, the New York Marathon on Sunday, or its upcoming iconic Thanksgiving Day Parade.

He said they prefer to orchestrate attacks “to hang on the hook for something” like the parades so it “maximizes the effects”

Victor Asal, a political science professor at SUNY's University at Albany’s Rockefeller College of Public Affairs and Policy, said the internet is increasingly radicalizing "lone wolf" terrorists and encouraging them to take action.

“We are seeing more and more of the inspired lone wolf, who maybe has been directed ... who has bought into someone’s ideology,” Asal said.

Addressing the Internet’s role in these attacks, Hoffman quoted his recent book, Inside Terrorism, noting that social media and the Internet allow terrorists to reach people more directly than in the past.

“This new approach by terrorists, using the Internet, amplified by social media, so now we are seeing serial incidents,” Hoffman said. “It has much greater resonance and traction because of the communicative power of social media.”

Asal, however, encouraged Americans to not give the terrorists what they want.

“Extremists want Americans to hate all Muslims," he said. "But we need to realize we are not going to discriminate against an entire group, just against extremism itself."