New age threats include weaponized drones delivered in “swarms” that could attack the White House or any place the president is. The problem, he explained, is that the agency’s agents and Uniformed Division are trained mostly to stop ground attacks.

“Distractions from the sky, whether planes or drones, create additional security complications for an obvious reason: Secret Service agents and officers cannot fly,” he warned in Protecting the President.

He said that terrorists have looked at drones “for a long time,” and that “the real threat comes from the more spectacular swarm attacks.”