That attack was atypical of the damage small commercial drones can cause, as Ulrike Esther Franke, a policy fellow at the European Council on Foreign Relations who has studied the use of drones, noted in 2016. A U.S. military Reaper drone, she noted, can hover for much of a day carrying 500-pound bombs; the Venezuelan interior minister said that the two drones used in the alleged attack were carrying about two pounds’ worth of plastic explosives. Those explosives caused injuries but no fatalities; still, the stampede that resulted shows the drones’ efficacy in another terror tactic of causing panic disproportionate to the actual damage inflicted. And it doesn’t take much to cause more serious damage; last summer, a commercial drone briefly knocked out power for more than a thousand people when it crashed into an electricity wire in California.

Top U.S. officials, including FBI Director Christopher Wray, have warned that America is vulnerable. Washington, D.C., for example, has what Department of Homeland Security officials have called “the most tightly controlled airspace in the country”; it’s illegal to fly drones anywhere in the District. And yet: In 2015, an off-duty government employee managed to crash a drone onto the White House lawn. Last November, a man was able to fly a drone over one football stadium and near another in California, with the aim of dropping political leaflets, despite legal prohibitions against flying drones near such events. (He was arrested and charged with a misdemeanor.) Cathy Lanier, the senior vice president and chief security officer for the National Football League, who also served as Washington, D.C.’s chief of police from 2007 to 2017, said that the ability to curb the threat of commercial drones “is very limited right now. The problem is that the popularity is growing exponentially … How do you identify the nefarious actor from the hobbyist?”

Drone swarms are going to be terrifying and hard to stop

Jaz Banga, the CEO and cofounder of Airspace Systems, a firm that works on air security to counter rogue drones, said “there’s really no comprehensive protection right now across the U.S.” Drones have to be registered to fly—and attach identifiers akin to a license plate—but it can be difficult to discern them in the air. Like the drone that crashed on the White House lawn, they can be too small or too low to spot with radar. And though the technology now exists to identify who is operating a commercial drone, drone operators are not yet required to use it. In the event that a rogue drone is detected, it’s generally illegal to shoot it down; ditto with jamming the radio or Wi-Fi signal controlling it, as the Venezuelans apparently did. And if law enforcement did so anyway, it could pose risks to civilians on the ground. The Federal Aviation Administration is working on rules to require identification; other defense measures would require changes to the law.