Invasive drones are snooping everywhere — here’s how they can be defeated.
Drones have proliferated everywhere in recent years, from underneath Christmas trees to major sporting events and even warzones. They’re cheap, easy to pilot, and have a heck of a lot more range than the Dollar Tree RC helicopters I grew up with.
But with that accessibility comes the reality that anyone can get their hands on a drone, and that drone can become a menace — spying with cameras or Wi-Fi sniffers, delivering hostile payloads, invading your space and your privacy.
In the U.S., there are laws meant to protect everyday folks from reckless drone operators, and by March 16, 2024, all FAA-registered drones will be required to broadcast their Remote ID and location — think of it as a license plate for drones, allowing the aircraft to be traced back to its pilot to ensure everyone is flying safely.
But there are still bad actors who don’t adhere to the rules, and drones smaller than 250g can fly unregistered. So how can we disarm a troublesome drone? There are a number of ways a rogue drone can be neutralized or brought down, from RF exploits to good ol’ fashioned “throw something at it” methods.
Disclaimer:
The information presented here is for educational purposes! If a drone is trespassing on your property or being a nuisance, report the drone operator to your local FAA flight standards district office and your local police department.
It is illegal to shoot at, maim, or interfere with any aircraft, including drones that don’t belong to you. Jamming or interfering with GPS signals is also illegal, as is interfering with most RF frequencies. Please exercise good judgment and extreme caution and check your local guidelines before you take drone justice into your own hands!
Nets
Sometimes a complex problem has a simple solution. One of the easiest and most consistent ways to bring down a drone is to disable the propellers, causing the drone to crash back down to Earth. The Tokyo Police Department’s interceptor drone, for example, drags a net through the air to catch the rogue drone by forcing a mid-air collision with the net.
An extremely effective DIY method of catching low-flying drones is a simple net gun. Modify a T-shirt cannon or an old potato cannon to use a net instead of the usual projectile, and you’ve got yourself a DIY drone wrangler! The tricky part is designing a launcher that encourages the net to spread out when launched. Like in shrimping, the net must be cast in a spreading motion with weights at the ends, to catch a drone and stop those props. Try designing a 3D-printed capsule that helps disperse the net, or try Crispyjones’ net gun or William Osman’s.
Lasers
When we imagine how to protect ourselves from the threats of the future, the answer is usually an enthusiastic “lasers, of course!” But how effective are lasers at defending against drones?
A drone is susceptible to extreme heat, especially if its wiring or LiPo battery gets compromised. However, a laser powerful enough to physically damage a drone is at least a Class 4 laser and your aim would need to be very steady.
If you’re determined to have a Death Star moment with the pesky drone buzzing your backyard, any laser you can get your hands on is more likely to mess with the drone’s cameras or IR sensors rather than melt it. Remember that shining a laser beam at any aircraft, including drones, is very illegal in the United States and could land you with hefty fines or even jail time.
Sensors
Most drones are loaded with sensors, from inertial measurement units (IMUs) to magnetometers to weather instruments like barometers for calculating altitude. Some of these sensors are considered the “payload” of the drone, recording data during flight for later analysis, but more often than not, these sensors feed into the flight controls of the drone, especially if it’s programmed for an automated flight path, or flying in a stabilized mode.
For example, DJI’s Mavic Mini drones have multi-direction time-of-flight (TOF) distance sensors that help prevent the drone from crashing into any solid objects. These sensors have an infrared (IR) emitter and receiver, sending out a pulse of infrared light, then measuring the time it takes for that light to be reflected back. Using that time, the sensor can calculate a precise distance from an object or surface, such as the ground or a wall. TOF sensors can also be used to 3D scan and map objects.
Of course, one drone’s safety feature is another person’s chance to exploit. With a bright enough near-IR flashlight to flood the sensor, or refractive material to scatter the light (don’t fly a drone over a swimming pool!), it is possible to dupe the TOF sensors into believing the drone is about to collide with an object. Depending on how the flight controls are configured, you can bias the drone into overcorrecting to avoid a collision, like a technological matador!
LiPo Battery
Lithium polymer (LiPo) batteries are common to most drone platforms. They have all the right characteristics making them the perfect choice as the power supply for unmanned vehicles, with their high energy density, quick discharge rate, and light weight.
LiPo batteries, however, do have drawbacks — like their propensity to burst into flames when punctured. If there’s one surefire way to bring down a drone, it is causing said drone to light itself on fire! If you decide to take the medieval route to take down a drone using a crossbow bolt or similar projectile, be aware that if you puncture the LiPo battery, the drone may cause a fire where ever it crash-lands.
GPS Jamming
There are two paths when it comes to messing with a drone wirelessly — attack its GPS signal or its radio frequency (RF) control signals. To choose your avenue of attack, study the type of flight path the drone is taking. Drones can either be controlled via a live operator or be programmed to follow an automated flight path. If it’s on a programmed path, it’s relying on GPS.
GPS jamming is highly effective — but extremely illegal — for stopping rogue drones. When a drone loses its GPS fix, it will usually rely on other sensors to maintain altitude, but will drift in the air until the operator intervenes or the drone lands itself in place.
GPS satellite signals are notoriously weak when they reach the GPS receiver, making it surprisingly easy to jam the signal. There are three GPS frequency bands known as L1, L2, and L5, at 1575.42, 1227.60, and 1176.45MHz. GPS jammers can be bought online for very cheap, but the problem is broadcast strength. If the drone is too far away, you’ll need a louder transmitter. Pick up an RF amplifier and a directional antenna to avoid jamming unintended targets.
GPS Spoofing
GPS spoofing is a trickier art form, but produces much more exciting effects when used on a drone. A commonly available software defined radio (SDR) transmitter and some open source software is all you need to produce a false GPS signal. The drone will try to correct itself based on where it was and where it thinks it currently is. This can throw the drone into an over-correction loop, where the sensors and the GPS are at war with one another in the flight controller module. It produces an effect much like “death wobble” on a skateboard, where the oscillations build up until you’re thrown off, or in the case of the drone, it’s sent crashing into the ground!
RF Jamming
GPS denial is a great trick in the anti-drone toolbag, but it won’t lock a drone operator out of control of the drone entirely. Instead, jamming the radio control signals is a reliable way to stop delinquent drone operators from buzzing your yard and annoying your dog.
Most drones operate on the 2.4GHz and 5.8GHz radio frequency bands, utilizing Wi-Fi, Bluetooth, and other analog and digital broadcast methods to transceive control, instrumentation, and video data. So the “easy” solution is to drown everything out on those RF bands, right?
Well, unless you’ve gotten your hands on a very expensive and very loud radio transmitter, you’ll need to go the clever route to jam a drone. Most drones utilize a technique called frequency hopping, which means they switch rapidly between several (usually eight) narrow slices of those RF bands, so they don’t interfere with other devices and drones in the area, but they’re still receiving the correct data.
Using an SDR, it’s possible to listen and figure out which narrow bands the drone is hopping between. Then, you can set up multiple smaller (and cheaper!) RF jammers on those step frequencies, so you’re jamming precisely, and thus need less power! It pays to work smarter not harder, especially in the realm of RF jamming.
RF Hacking
Really want to crack the code? An SDR can retransmit captured RF signals to cause confusion in a replay attack. Or, a Wi-Fi deauth attack can disconnect a drone from its controller. You could even try to decode the signals with GNU Radio and then send your own commands to hack or spoof the drone’s onboard computer. Every drone’s different, so you’re on your own here.
This article appeared in Make: Vol 87. Subscribe for more great articles.
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