Drone, meet counter-drone ...

A boom in consumer drone sales has spawned a counter-industry of start-ups aiming to stop drones flying where they shouldn't, by disabling them or knocking them out of the sky.

Firms are developing techniques - from deploying birds of prey to firing gas through a bazooka - to take on unmanned aerial vehicles that are being used to smuggle drugs, drop bombs, spy on enemy lines or buzz public spaces.

The consumer drone market is expected to be worth $5-billion by 2021, according to market researcher Tractica. The average drone in the US costs more than $500 (R7000) and packs features such as high-definition cameras and built-in GPS.

Millions of consumers can fly high-end devices - and so can drug traffickers, criminal gangs and insurgents. Drones have been used to smuggle mobile phones, drugs and weapons into prisons, in one case triggering a riot. One US prison governor has converted a bookshelf into an impromptu display of drones his officers have confiscated.

Armed groups in Iraq, Ukraine, Syria and Turkey use off-the-shelf drones for reconnaissance or as improvised explosive devices, says Nic Jenzen-Jones, director of Armament Research Services, a consultancy.

A booby-trapped drone launched by Islamic State militants killed two Kurdish Peshmerga fighters and wounded two French soldiers in October near Mosul. The use of drones by such groups is likely to spread, says Jenzen-Jones.

"There's an understanding that the threat can migrate beyond existing conflict zones," he said.

This is feeding demand for advanced technology to bring down or disable unwanted drones. At one end of the scale, the Dutch national police recently bought several birds of prey from a start-up called Guard From Above to pluck unwanted drones from the sky.

Other approaches focus on netting drones, either via bigger drones or by guns firing a net and a parachute via compressed gas.

Some, like Germany's DeDrone, take a less intrusive approach by using a combination of sensors - camera, acoustic, Wi-Fi signal detectors and radio frequency scanners - to passively monitor drones within designated areas.

Newer start-ups, however, focus on cracking the radio wireless protocols used to control a drone's direction and payload to then take it over and block its video transmission.

Singapore's TeleRadio Engineering uses radio signals in its SkyDroner device to track and control drones and a video feed to confirm targets visually.

DroneVision of Taiwan, meanwhile, says it is the first to anticipate the frequency hopping many drones use. Its anti-drone gun - resembling a rifle with two oversized barrels, coupled with a backpack - blocks the drone's GPS signals and video transmission, forcing it back to where it took off via the drone's own fail-safe features.

Clients range from intelligence agencies to hotels. DroneVision, for example, helped local police down 40 drones flying around Taipei 101, one of the world's tallest buildings and a magnet for drone users, in a single day.

In the Middle East, upscale hotels are talking to at least two companies about blocking drones from taking shots of their celebrity guests lounging at the pool or in their bathrooms.

And even while the military, Jenzen-Jones says, may have the capability to bring down drones, demand is shifting to nimbler, more agile devices to cope with attacks using smaller off-the-shelf devices.

"The key is looking for systems that are scalable, lightweight and easily deployable," he said.

DroneShield, an Australian company, says it has sold its drone detection equipment to an Asian national security agency it declined to identify, and the Turkish prime minister's office.

The problem is that regulations on the use of drones - and about countering them - are still in their infancy. In countries like the US and Australia, for example, drones are considered private property, and they can only be jammed by government agencies.

"Mitigation capabilities," says Jonathan Hunter, CEO of Department 13, "are therefore limited."

Oleg Vornik, chief financial officer of DroneShield, however, says: "This is expected to change shortly as governments start to recognise that critical infrastructure facilities such as airports need to be able to defend themselves against drones."

In the US, the Federal Aviation Administration is testing various counter-drone technologies at several airports.

London will next year host the world's first two conferences on counter-drone technologies, says Jenzen-Jones. But there will also likely be consolidation.

DroneShield's Vornik says the company has counted 100 counter-drone start-ups, and is talking to more than a dozen of them as potential acquisition targets.

It's too early, Vornik says, to see evidence of moves to get around anti-drone technology. But Amazon.com last month tested deliveries in the UK via drones, and published a patent describing how it might defend drones from threats ranging from a bow and arrow to signal jammers.

- Reuters