An Army soldier launches a Raven hand-held drone in Iraq.

WASHINGTON: Sometimes small is beautiful. Sometimes small is lethal. While China and Russia are researching stealthy and armed drones, the drunk intelligence analyst who landed a Chinese-made mini-drone on the White House lawn in last month may be the more worrying sign of things to come.

Afghan and Iraqi guerrillas kludged together murderous roadside bombs with scavenged or homebrewed explosives triggered by cellphones or garage door openers, killing more Americans than any of Saddam’s Scud missiles or main battle tanks. What might similarly ingenious insurgents do with off-the-shelf drones?

“We’re seeing capabilities that were previously the monopoly of major military powers are now accessible…to non-state actors, even individuals,” said Kelley Sayler. She’s an associate fellow at Center for a New American Security and author of a report out this morning, “A World of Proliferated Drones.” (CNAS provided us a copy in advance).

“There’s been a lot of discussion around town, particularly as relates to drones in the national security space about high-end drones,” Sayler told me. “We didn’t really see there being discussion on the range of systems that are available…particularly given the availability of low-end systems, hobbyist drones, even commercial drones.”

The biggest danger in the medium term: swarming technology. As drones get not only smarter but cheaper, an enterprising adversary could buy a bunch and release them all at once, with the drones using insect-like artificial intelligence to converge on their target. Lots of little threats carrying lots of little bombs can add up quickly.

“Particularly if you’re looking at systems that can truly navigate autonomously, using those systems en masse is going to enable you to neutralize a much larger target,” Sayler said, “[and] it’s going to be more difficult to defend against because some of the lower end solutions like shooting the thing out with a shotgun might not necessarily be feasible.”

“Drones will enable airborne IEDs [improvised explosive devices] that can actively seek out US forces, rather than passively lying in wait,” Sayler wrote in the report. “Indeed, low-cost drones may lead to a paradigm shift in ground warfare for the United States, ending more than a half-century…in which US ground forces have not had to fear attacks from the air.”

Sophisticated drones are definitely part of that future threat, she said. But they require the resources of an advanced nation-state to develop and operate, and nation-states tend to be less murderously inventive than low-rent irregulars.

“When we are looking at the higher end systems we are seeing something that would be akin to missiles or manned fighters,” Sayler said. “When you’re looking at traditional state use, you are probably going to find more traditional and restrained uses.”

Guerrillas and terrorists, by contrast, generally have much less capability than nation-states, but they are more likely to use what they have in unexpected ways. Hezbollah has fired a drone with almost 60 pounds of explosives at Israel, although it was detected and shot down. Smaller drones are harder to detect, and states less vigilant than Israel — which has anti-missile systems constantly stopping rockets — might not be set up to detect them.

“We’re more looking at a threat that is rising from unanticipated use where US troops or allied troops are not particularly expecting a threat…. and therefore your countermeasures are not really in place,” said Sayler.

The simplest use of off-the-shelf drones would be to spy on US forces. That kind of low-rent reconnaissance could provide a significant tactical advantage without requiring any modifications. With a little jury-rigging, many widely available drones could carry five to 10 pounds of explosive. That’s hardly the same as a vehicle-flipping 500-lb roadside bomb, but it’s enough to kill.

The good news is that if you are aware of the threat, there are plenty of ways to stop it. “If you know these systems are coming … you can shoot them down with a shotgun,” Sayler said. Or, if you’d like to fight robotic fire with fire, there are specialized “drone-hunting drones” that catch unauthorized flying objects in a net.

The easiest way to defend large areas for a long time is jamming. At the very least you prevent the enemy drone from transmitting back intelligence to its operators. For the majority of drones flying today that navigate using either continuous GPS signals or constant remote control by a human, jamming can stop them in their tracks.

The immediate problem is what else you’ll jam. In a wilderness or free-fire war zone, the electronic collateral damage might not matter. In urban counterinsurgency, peacekeeping, or policing, however, you’ll turn the local population against you quickly if you’re constantly scrambling their cellphones. Set the jammers to avoid civilian signals like phones and police radios, and you can bet the bad guys will convert their drone controls to use the same frequencies.

The longer-term problem is that drones are getting smarter and more autonomous. “In the next few years we’re going to see technologies like sense-and-avoid systems being incorporated that allow the drone to autonomously navigate around objects,” said Sayler, reducing the need for a GPS signal or constant human supervision. That makes the coming swarm much harder to stop.