Today's vehicle terror attack in Barcelona represents the type of low-tech assault that is very hard for authorities to prevent, Buck Sexton said on "Outnumbered."

The former CIA counterterrorism analyst said ISIS favors these types of attacks for that reason, directing sympathizer by "remote control."

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Sexton explained that in cases, ISIS-inspired terrorists were found to have received key information from others to help them carry out an attack. 

"It's very difficult to prevent a low-tech attack like this, which has can also be a mass casualty low-tech attack," he said. 

At least two people were killed and 20 injured when a vehicle hit a crowd of people in a popular area of Barcelona, Sky News and local media reported.

A van struck pedestrians in the Las Ramblas tourist area, in the center of the city in what local police are calling a terrorist attack.

The driver fled the scene and police responded to a hostage situation at a nearby restaurant.

Watch his analysis above and read more on the attack, here.

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