The market, and the military, have yet to settle on the best way to stop a drone.
Relatively small, easy-to-acquire drones have been implicated in everything from attempted political assassinations, to airspace incursions that have forced major airports to shut down, to smuggling contraband into prisons. The widespread availability of easy-to-pilot drones with good camera capabilities raises security issues that have fueled a growing market for technology to stop such remotely piloted aircraft.
While regulations for the flying of drones are far more settled in 2020 than they were in 2010, the regulatory landscape for technology to stop them is more unsettled. While many technologies exist that can variously track, identify, and disable drones in flight, these countermeasures risk either jeopardizing communications, violating Federal Communications Commission rules, infringing privacy, or causing inert robots to crash to the ground. Separate from this, but confounding the problem, security concerns around the testing of counter-drone tools mean that useful comparison data is hidden from the public, and often unavailable to government officials.
What is a ‘drone’ anyway?
Part of the problem, broadly, is that “drone” is an expansive category, a catch-all phrase for vehicles that share the lack of an on-board human pilot. The flying body of a drone can be more technically defined as a “remotely piloted aircraft,” or an “unmanned aerial vehicle.” In conjunction with other aircraft, as well as ground control stations and other support, the term is sometimes a “remotely piloted system” or an “unmanned aircraft system.” Other names abound.
Beyond the confusing nomenclature, drones encompass a range of aircraft sizes, forms, and capabilities, all of which change how effective any given counter-drone approach can be. Drones include everything from relatively cheap hobbyist toys to multi-million-dollar plane-sized aircraft with flight times measured in days, not minutes.
At a certain size—that of Reapers, Global Hawks, and the like—the vehicles can be tracked easily by radar. For these large craft, counter-drone technology is mostly the same as anti-plane technology, with missiles and other systems built to shoot down planes or, sometimes, helicopters totally applicable.
The counter-drone market, as a category, sometimes concerns these larger vehicles. Without an onboard human pilot, even the largest of drones are vulnerable to signal disruption, GPS spoofing, or other means of electronic warfare, which seek to exploit the remote nature of control and turn it into a unique vulnerability.
Defining the drone threat
Much of counter-drone technology is designed to work, broadly, against small- and medium-sized hobbyist, commercial, or industrial drones. Some of the devices used are also applicable against larger and more sophisticated, military-style vehicles, but as already noted, if the drone is big enough conventional anti-air systems work.
The reason for all the focus on small drones, here defined especially as those weighing up to 55 pounds, is that they do not register on conventional anti-air systems. Radar systems are built to track large, fast-moving aircraft. To avoid false alarms from flocks of birds, many radar systems filter out small returns as noise. Radar also struggles with slower aircraft and with aircraft flying low to the ground—which was how a man was able to fly a gyrocopter onto the lawn of the Capitol in April 2015 and reveal a gap in existing radar detection. That gyrocopter was a crewed vehicle with an onboard pilot, but it’s a good fit for the upper bound of drone size, and some of the flaws of detection.
So far, the highest profile threat from drones is that of a drone carrying an explosive. From a small grenade to a shaped charge to a larger explosive payload, putting a bomb on a drone offers someone a few advantages over placing it or launching it with a more conventional weapon. The most immediate advantage is that, by and large, most places, people, buildings, and vehicles are less protected on top, and a drone-delivered bomb can be especially effective if flown overhead. Another reason to use a drone is that it offers a degree of control and precision in targeting, especially if the drone has a camera.
Bomb-carrying small drones have been used in Iraq, Ukraine, Syria, and even implicated in an assassination attempt on Venezuelan President Nicolás Maduro. It is the top-line fear of most security forces tasked with defending against drones, and it is a threat that has a special place in the marketing of counter-drone tools. There are also special-designed grenade-carrying drones, as well as one-way drone-like missiles, marketed to militaries and built for use in combat.
Beyond direct, deadly attacks, small drones can be used in a variety of ways to bypass existing, terrestrial defenses. Most simply, hobbyist drones offer an aerial camera, allowing people to scout out a facility from above and at a distance, before finding a way in or a path around a defense. This filming can also be done in real time, so a group of people could benefit from an airborne overwatch as they sneak around.
Small drones are also often cheap enough that they can be used as somewhat expendable smuggling tools. This has in many reported cases come in the form of drones used to smuggle contraband into prisons. Drones have also disrupted sporting events, like the time a drone carrying an Albanian flag flew onto the pitch of a soccer match between Serbia and Albania in 2015.
Small drones also pose serious safety issues at airports, where a commercial airliner striking a drone or sucking one into a jet engine could have disastrous consequences. Over two days in 2018, a series of drone sightings at Gatwick Airport shutdown the busy airfield, stranding 140,000 people. No drone was ever confirmed to be found, though multiple counter-drone technologies were brought to the scene and the airport has invested in counter-drone tech going forward.
Beyond documented incidents, the range of possible small drone intrusions is only limited by the bounds of imagination: One could conceivably use a small drone to approach and break into a sensitive Wi-Fi network or pilot one onto the roof of a car and spoof its GPS system.
The range of counter-drone technology
Finding and acquiring the right tool to detect, and mitigate, a small drone intrusion depends a lot on the kind of attacks specifically feared. It means something very different to protect a convoy on patrol from quadcopters in an ambush than to keep an office free of unwanted aerial surveillance.
In response to this broad range of possible attacks, the counter-drone market is a vast field with literally hundreds of specific products.
The single best source of reporting and tracking on the counter-drone market is the Center for the Study of the Drone at Bard College. A survey of the existing counter-drone market by the Center published in February 2018 found 235 counter-drone products. An updated study, published in December 2019, found at least 537 unique counter-drone systems.
The center classifies a counter-drone system by three major criteria: How it finds a drone, what it does once it finds a drone, and on what platform the system is installed.
Platform is the most simple category: Broadly speaking, counter-drone systems are either fixed on the ground, mobile on a ground vehicle, hand-held by a single person, or mounted on another drone.
Finding a drone, or more precisely, detecting, tracking, and identifying a drone can be done in a number of ways. Radar is a popular method, with counter-drone radars specifically calibrated to find smaller drones and paired with software and algorithms that enable them. Drones can also be detected by what they emit, from radio frequencies to sound. And drones can be seen, either with electro-optical or infrared cameras. Some counter-drone systems combine these features to build a more comprehensive tracking tool.
If a counter-drone system is designed to interfere with the drone’s operations in some way, it’s an interdiction tool. The possibilities include, but are hardly limited to, jamming the drone’s radio signal, jamming its satellite link, feeding it incorrect location information, incapacitating its cameras with light or lasers, frying its electronics with microwaves, or physically impeding it in some way, like with nets or even specially designed anti-drone ammunition. (Normal bullets would also fall under this category.)
There are also, in the niche of counter-drone drones, collision drones, which are specifically designed to collide with the target vehicle.
Geofencing is a kind of drone-threat mitigation that relies on limits programmed into drones by manufacturers, based on data about flight restrictions made publicly available. Geofencing works by drawing a perimeter defined by global positioning coordinates. A drone programmed to adhere to the geofence and operating with the latest information will not fly into a geofenced area. It’s a good and popular first step to prevent the misuse and loss of hobbyist or commercial drones, but because the technique requires both onboard knowledge of what is prohibited and a global positioning system, it can be defeated by bypassing one or the other. For hobbyists who build their own drones, geofencing is even easier to bypass: Just don’t include it in the design. Even for people who don’t intend to break a law with their drones, failing to update software before a flight could lead to a drone flying into a prohibited space.
As a matter of policy, geofencing is a good first line for keeping accidental drone intrusions to a minimum. It should not be seen as more than that.
Clear skies, unclear legal precedents
The makers of most counter-drone systems only provide prices available on request, which makes open-source analysis of the market difficult. For the most part, counter-drone systems are expensive, out of reach of almost all people, most businesses, and some governments. Securing the skies against the possibility of a threat must be weighed against the cost of acquiring and then using the system. Care must be taken, especially, to make sure that the drones targeted pose a threat and are not just errant hobbyists unaware that they are piloting their toy into contested skies.
For airports, state, and local law enforcement, the regulatory landscape for adopting counter-drone tech is unsettled, and specifically risks running afoul of communications rules regarding the radio frequency spectrum. In a September report, the Congressional Research Service observed that the Federal Aviation Administration “has warned that [counter-drone] technologies pose potential risks to manned aircraft and to surveillance, navigation, and communications signals used by air traffic control.” The report notes that an interagency legal advisory from August of this year “cautioned nonfederal public and private entities that UAS detection technologies could run afoul of a wide gamut of federal statutes and regulations pertaining to privacy and the use of radiofrequency spectrum.” Technologies to disable drones face similar regulatory uncertainty: “Systems designed to interdict drones could violate federal laws and regulations regarding aviation safety and security and prohibitions against jamming or interfering with radio communications or impeding navigation through the airspace,” the report finds.
In short, anything that threatens to hurt an aircraft, including drones, risks running afoul of FAA rules, and anything that uses the spectrum to jam or interfere with drone communications could run afoul of FCC rules and protected parts of the spectrum. So far, the only legal exceptions for counter-drone use in the United States apply to Homeland Security and federal law enforcement. Which means that while individuals, companies, and state or local agencies may purchase some counter-drone tools, using them comes with additional risk, and without clear legal protection. Projectile weapons come with their own set of risks, especially when operated in areas with civilians present. Counter-drone systems that listen to drone radio traffic may violate laws against warrantless wiretaps. Sending a drone false coordinates could violate the Computer Fraud and Abuse Act.
Given the complexities and opacity of the counter-drone market, it is likely there is space for further congressional action, both funding studies on the effectiveness of counter-drone tools, and on establishing rules and standards for their use. While there is some overlap in use-cases between military, law enforcement, and other customers, the means available and the laws regarding those means can vary greatly between military, law enforcement, and civilian contexts. Counter-drone operations may best be tied to bomb squads or explosive ordnance disposal teams, as it can be hard to know if an incapacitated drone is carrying a deadly payload from a distance.
In looking to craft policy guidelines for the use of counter-drone systems, policymakers should consider the possibility of catastrophe if a drone does manage to cause harm. Nuclear reactors, which have been buzzed by drones, are designed to withstand the impact of larger aircraft, but there may still be vulnerable parts of the infrastructure worth protecting against drone intrusion. Likewise, airports remain especially vigilant against the possibility of a drone damaging a plane on takeoff or landing. The USDA Forest Service has warned that drones flying in the area of wildfires pose a risk to aircraft fighting those fires.
Having the tools on hand to prevent harm, instead of simply trusting that every person with a drone will always follow best practices, is likely an essential part of the bargain of living with cheap drones in the future. In crafting policy to manage flying robots, and protect people, it is important that the countermeasures chosen do not become worse than the threat they are designed to stop.
Kelsey Atherton is a military technology journalist based in Albuquerque, New Mexico. His reporting has appeared in Popular Science, Breaking Defense, and The New York Times.