How to tell if a drone is stalking you | Science News for Students

How to tell if a drone is stalking you

Researchers can now detect when a flying robot is streaming video of you or your home
Feb 20, 2018 — 6:30 am EST
flying drone
A new technique can show when a sneaky robot is streaming video of you or your home.

Now there’s a way to tell if you’re being spied on by eyes from the sky.

Researchers have developed a method to find out what a drone — a flying robot — is recording. And they can tell without having to translate the video information that the device is streaming to its pilot. This technique, described January 9 on the site, could help military bases detect unwanted robotic snoops. It also could help civilians protect their privacy as more drones take to the air.

“People have already worked on detecting [the presence of] drones,” says Ahmad Javaid. He studies cybersecurity — or how to keep computers secure from spies — at the University of Toledo in Ohio. “But no one had solved the problem of, ‘Is the drone actually recording something in my direction?’”

Ben Nassi is a software engineer. That’s someone who develops computer programs. He works in Israel at Ben-Gurion University of the Negev. The images streaming from a drone are made up of tiny lighted areas, called pixels. Nassi’s group realized it could change how objects look to a drone. When something it’s recording changes (say, switches to a different color), the stream of encrypted data that the drone broadcasts to a computer (that controls it) also will change. (Encrypted data are those that have been put into a secret code.)

The drone sends those data via Wi-Fi. When the pixels change color, the data need to change, too. The more pixels that change from one video frame to the next, the more data the drone sends per second. So if a scientist could rapidly switch the appearance of a person or house, the drone’s pixel information would switch as well. That would require more data. And the scientists could then track whether the appearance changes corresponded to higher drone-to-phone Wi-Fi traffic. If they do, that suggests the drone might be recording you.

Spotting drone signals

Nassi’s team decided to test this idea. They covered a house window with a special film. It could switch between clear and nearly solid white. To do that, they merely had to point a remote control at it. The researchers either flickered this “smart” film back and forth every two seconds or left it clear. Then the scientists aimed a drone with a video camera at the window from 40 meters (130 feet) away and hit “record.”

The flickers should show up on the drone’s video as pixel changes. To find out if it did, the scientists pointed a scanner at the drone that could detect radio waves. Those were the Wi-Fi signals being broadcast by the drone. And sure enough, the drone’s Wi-Fi traffic spiked whenever the smart film flickered. That confirms that a simple radio scanner can tell when a drone is videotaping a window.

Story continues below image.

Scientists stretched a smart film across a window. It can flip from transparent (green) to nearly opaque (red). When the window flips back and forth between those two colors, more pixels in a drone's video change between frames. This increases the drone's outgoing Wi-Fi traffic (stimulus interval), compared to when the smart film stays clear (idle interval).
B. Nassi et al/ 2018

Using radio equipment may not be strictly required. It’s possible to intercept Wi-Fi signals with a laptop or other computer with a wireless card, says Simon Birnbach. He’s a computer scientist not involved in the work. He works in England at the University of Oxford.

In a second test, a drone recorded someone from about 20 meters (66 feet) away. This person was wearing a strand of LED lights. (These are also known as light-emitting diodes.) Every five seconds, the lights flickered on and off, or just stayed off. Data streaming from the drone’s camera spiked whenever the lights flickered. These data show that scanning data from the drone could detect surveillance of even an individual.

This technique to identify a drone camera’s target is “a very cool idea,” says Thomas Ristenpart. He’s a computer scientist not involved in the new study. He works at Cornell University in Ithaca, N.Y. Still, he says, the researchers need to test whether this technique will work for more than a house window or flashing lights. “I don’t think anyone is going to want to wear a [light-up] shirt on the off chance a drone may fly by,” he quips.

Javaid agrees. This prototype system must be more user-friendly, he says. For home security, he imagines a small device with a flashing light stuck to a window. It could intercept a passing drone’s Wi-Fi signals. That could alert the homeowner when a snooping drone flew by.

Drew Davidson works as a computer scientist at Tala Security, Inc. in Dallas, Texas. He was not involved in the new work. He points out that even if you knew a drone was nosing around, you may not know who was controlling it. “It’s sort of the equivalent of knowing that an unmarked van pulled up and waited outside of your house,” he says. “[It’s] better to know than not,” he says. Still, he adds, it may not be enough for the police to track down the snoop.

Power Words

(more about Power Words)

arXiv     A website that posts research papers — often before they are formally published — in the fields of physics, mathematics, computer science, quantitative biology, quantitative finance and statistics. Anyone can read a posted paper at no charge.

colleague     Someone who works with another; a co-worker or team member.

computer program     A set of instructions that a computer uses to perform some analysis or computation. The writing of these instructions is known as computer programming.

diode     An electronic part that works like a one-way valve for electric current.

drone     A remote-controlled, pilotless aircraft or missile.

engineer     A person who uses science to solve problems. As a verb, to engineer means to design a device, material or process that will solve some problem or unmet need.

internet     An electronic communications network. It allows computers anywhere in the world to link into other networks to find information, download files and share data (including pictures).

LED     (short for light emitting diode) Electronic components that, as their name suggests, emit light when electricity flows through them. LEDs are very energy-efficient and often can be very bright. They have lately been replacing conventional lights for home and commercial lamps.

pixel     Short for picture element. A tiny area of illumination on a computer screen, or a dot on a printed page, usually placed in an array to form a digital image. Photographs are made of thousands of pixels, each of different brightness and color, and each too small to be seen unless the image is magnified.

prototype     A first or early model of some device, system or product that still needs to be perfected.

radio waves    Waves in a part of the electromagnetic spectrum. They are a type that people now use for long-distance communication. Longer than the waves of visible light, radio waves are used to transmit radio and television signals. They also are used in radar.

scanner     A machine that runs some sort of light (which includes anything from X-rays to infrared energy) over a person or object to get a succession of images. When a computer brings these images together, they can provide a motion picture of something or can offer a three-dimensional view through the target. Such systems are often used to see inside the human body or solid objects without breaching their surface.

smartphone     A cell (or mobile) phone that can perform a host of functions, including search for information on the internet.

software     The mathematical instructions that direct a computer’s hardware, including its processor, to perform certain operations.

software engineer     An engineer who designs and works with computer programs.

Wi-Fi     A wireless technology that networks various electronic devices (such as cell phones and laptop computers); it allows them to share the same modem for Internet connections by using radio waves.


Journal:​ ​​ B. Nassi et al. Game of Drones - detecting streamed POI from encrypted FPV channel. arXiv:1801.03074. Posted online January 9, 2018.