BASEL, Switzerland — In the battlefields of Syria and Iraq, the Islamic State group became infamous for its spectacular variations on explosive vehicles. For attacks in the West, it has suggested a simpler method, encouraging followers to use regular vehicles to kill people on foot.

Experts say attacks in which cars or trucks are driven into popular pedestrian areas present a unique challenge for law enforcement officials as they are nearly impossible to predict and easy to pull off. They require no advanced training, no specialized materials. Almost anyone can own or rent a vehicle.

Some feel that these low-tech, lone wolf operations can have the same psychological impact as larger, more sensational attacks.

Four people were killed and dozens wounded Wednesday in London with this tactic — the worst attack on British soil since the transport network bombings on July 7, 2005.

Charlie Winter, a senior research fellow at the London-based International Centre for the Study of Radicalisation and Political Violence, says what makes such attacks so frightening is the relatively low barriers to entry. The method was embraced by al-Qaida before being revitalized by IS.

“It makes for a very effective unsophisticated high impact, very frightening form of an operation,” he said. “You don’t need to know someone who can make you a bomb or buy you a gun in order to carry out an attack. It’s a very difficult thing to fight against. There is no quick fix.”

British authorities on Thursday identified Khalid Masood as the man who mowed down pedestrians with an SUV and stabbed a policeman to death outside Parliament. The British citizen wasn’t on a terrorism watch list although he was once investigated for extremism. IS claimed responsibility for the attack, saying he was a “soldier” that answered its call to attack nations in the coalition fighting IS in Syria and Iraq.

Rita Katz, director of the SITE Intelligence group, says it is almost impossible for law enforcement agencies to stop IS-inspired attacks, especially vehicular-style ones like the one in London. Since 2014, this simple but effective attack has been promoted in IS propaganda online.