Transcript for US cities increase security after deadly London attack

Security here at home is stepping up in response to the attack and Pierre Thomas has more from Washington. Good morning, Pierre. Reporter: Good morning, Michael. Some major cities including new York are stepping up security at landmarks but this morning our sources are saying there's no intelligence pointing to a specific plot here at home. But make no mistake stabbings and attacks by vehicles are among the biggest concerns law enforcement officials have in terms of terror. Four different bulletins warning about attacks involving vehicles or knives. What ISIS has been calling for and it's working. There have been at least 14 vehicle attacks since 2014 including the horrific massacre in nice, France, the Berlin Christmas market nightmare and here at home at Ohio state when a suspect hit pedestrians and then stabbed multiple people, Michael. Pierre, how would the U.S. Law enforcement, how are they responding? Reporter: The good news is U.S. Law enforcement has been thinking about and preparing for these kind of attacks for years. In New York City, during the times scare new year's celebration dump trucks and others were put up to prevent access and dump trucks were used at the Republican national convention. The bad news, every day cars are traveling along streets full of pedestrians. How do you protect those people? We'll have a lot more on the

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