From public nuisance to major threat if they ball into terrorist hands.

Drones — remotely-controlled unmanned aerial vehicles (UAVs) — come in any number of sizes and configurations. Some are weapons of war, such as the MQ-9 Reaper, whose pilots have killed hundreds of terrorists in the Middle East and Southwest Asia. The MQ-9 has a 66-foot wingspan and is 36 feet long. Some are toys like the 16-inch toy quadcopter your neighbor’s kid flies. Most are remotely-piloted while some are programmed to operate autonomously.

UAV’s perform countless tasks. They can be used to map forests, inspect industrial equipment that is spread over many acres and which can be hundreds of feet tall. Just last week, Australian lifeguards unpacked a drone in about two minutes, attached a flotation device to it, and flew it almost a half-mile offshore to drop the flotation device to two swimmers fighting big waves, saving their lives. The lifeguards couldn’t have rowed or swum out to them that quickly.

Many nations’ militaries are buying drones by the hundreds and terrorists are either buying or manufacturing their own and arming them with explosives and more. Millions of unarmed civilian drones are sold every year.

The threat of weapons and espionage equipment borne by drones is evolving quickly.

On New Year’s Eve, and on at least two occasions since, the Russian airbase at Hmeimim in Syria has been attacked with drones, sometimes operating in swarms. The Russians, as you’d expect, deny that the drones caused any damage but the Wall Street Journal reported on January 15 that the New Year’s Eve attack killed two Russian servicemen, injured ten more and damaged six aircraft. Those drones were monoplanes reportedly powered by small gasoline engines and operated from dozens of miles away.

The Russians, like our military and civil defense forces, face a threat from drones. As the Washington Post reported on January 13, D.C.’s airspace is crowded and highly restricted. Yet there is a growing number of drone violations of closed airspace occurring over military bases and other government facilities. In January 2015, one crashed on the White House lawn.

Even after a person operating a drone does something illegal — such as flying into the controlled area around the White House — it’s impossible to tell whether he’s just having fun or has murderous intent. Is it a knucklehead seeking a thrill by landing on the White House lawn or being flown by terrorists trying to use the drone to carry a bomb? It’s only possible to know after a drone has been forced down — or it delivers an attack — that we can know.

The only exception to that is if intelligence indicates a lethal attack is intended, and that isn’t always sufficient to stop the attack before it happens.

There are a lot of elements to UAV flights that prevent detection and interception. Drones are so small that they don’t appear on radar and they usually fly below radar coverage. Their infrared signatures are too small to detect.

The FAA licenses drone pilots, but very few drone operators are licensed. It requires that any drone over .55 pounds in weight be registered. (The weight limit for civilian drones is 55 pounds.) Millions are not registered. The FAA requires that non-industrial drones operate only within line of sight of the operator. That, too, is an easily-violated regulation.

In short, the FAA is pretty hapless. It has absolutely no control of people who intend to violate the law, especially terrorists. Companies such as Amazon, which are trying to create drone delivery systems for those who can only function with instant gratification, are trying to work out systems that satisfy the FAA.

Defenses against drones are few. Even with radar or infrared tracking, both of which usually don’t work, military and law enforcement people can’t shoot them down in or around cities, airports, and sports stadia and such because the shots that miss — and there will be plenty of them — can kill those in the line of fire. It would be nice to have a directed energy weapon that could slice and dice drones in the air, but we don’t have one yet.

The most obvious defense is jamming the drone’s controls, possibly taking over and flying the drone to crash it somewhere it can’t do any harm. But drones are usually controlled in two frequency bands that are dominated by other devices. Some commonly sold drones are controlled in the 800-900 MHz band that is also used by cellphones. Jam that band and you jam the cellphones. Other drones are controlled around the 2.4 GHz and 5.8 GHz bands. Most home and business WiFi systems operate around 2.4 GHz.

If an intelligence agency determined that a drone attack was imminent, and gave others sufficient time to deploy the equipment, jamming could work regardless of the inconvenience to cellphone and WiFi users. But that presumes that some innovative terrorist hadn’t found a way to fiddle the frequencies controlling his drones to avoid the jammer.

Otherwise? Well, otherwise we’re entirely unprepared to deal with terrorist attacks using drones. If you’re keeping score, I predicted several drones-as-bomber attacks this year. What was done by the people who attacked the Russian airbase in Syria can and will be done by others.

The least harmful result of the drone epidemic will probably be a swarm of Amazon.com drones buzzing around our residential communities delivering packages and annoying the hell out of anyone who wants to sit quietly on the porch, sipping single malt and smoking a very good cigar.