South Korean researchers have invented a new anti-drone technology, called Tractor Beam in a nod to "Star Wars," that can use fake GPS signals to fool dangerous drones, commandeering them and flying them to a safe landing site.

Crucially, the inventors discovered how to evade the fail-safe modes of various consumer drones, overcoming a major hurdle to earlier attempts at safe drone hijacking. Drones automatically enter an emergency fail-safe setting when their GPS system fails, leaving it when they recover GPS signals. Through software simulations and hands-on field experiments, the researchers showed that Tractor Beam, a device and associated algorithms that can inject GPS signals into drones based on their type, is able to thwart this mode in four real-world consumer drones: the DJI Phantom 3, DJI Phantom 4, Parrot Bebop 2 and 3DR Solo.

"I believe we are the first one to investigate the individual fail-safe mechanism," Yongdae Kim, a researcher at the Korea Advanced Institute of Science and Technology and a co-inventor of the technology, explained to The Academic Times. "The GPS hijacking should be implemented differently depending on both GPS fail-safe flight mode and behavior after GPS recovery. We show that all four types of drones can be hijacked."

The patent application was published by the U.S. Patent and Trademark Office on Feb. 18. It builds on a 2019 paper from ACM Transactions on Privacy and Security.

The innovation comes as security experts have warned about the rising threat of drone terrorism. In recent years, Islamic State operatives have reportedly used drones to attack Kurdish fighters and U.S. forces in Iraq, and in 2015, an anti-nuclear protester flew a drone laden with radioactive sand to the roof of the Japanese prime minister's official residence. In a report this year, the Department of Defense cited the "exponential growth" of drones as a critical new threat to its operations.

On a webpage describing their candidate invention, the research team outlined the shortcomings of other anti-drone strategies. Although rogue drones can be captured with net guns, the range of those guns is very limited, potentially delaying or jeopardizing the response. Both radio signal jamming and laser attacks can stop drones in their tracks, but they leave the dangerous unmanned vehicles in place, where they could still cause harm. The Tractor Beam, on the other hand, can remotely redirect drones to a new location, where any damage they cause would be minimal.

The use of fake GPS signals to fool devices is known as GPS spoofing. "GPS messages for commercial use are not 'authenticated,' meaning that if you can 'precompute' the location and the current time of GPS satellites, an attacker can generate their signal," Kim explained. The GPS receivers of the drones he tested could not tell the difference between legitimate signals and spoofed signals. When they selected spoofed signals, those receivers miscalculated the velocity or location of drones.

The team found that different commercial drone manufacturers enter different fail-safe flight modes and different fail-safe recovery operations. This influenced the GPS hijacking strategies that they chose. Kim cited the example of the two DJI drones. When these devices lose GPS signals, they check to find whether there is a new signal. Once they sense it, they use it to recalculate their location and speed. "The attack can simply inject stronger signals than the ones generated by the satellite, in order to deceive the DJI drones," Kim explained.

Tractor Beam, though powerfully named, has so far only been validated in consumer drones. "Theoretically, it can be used for military drones as well," Kim said. "However, we have not tested or investigated military drones, as we were not able to obtain them."  

Kim and his co-inventors recognize the risks created by their innovation. If Tractor Beam fell into the wrong hands, rogue actors could use it to undermine legitimate drone operations, mirroring the very problem it was designed to solve. "We are working on defense mechanisms as well," said Kim. "Better design of fail-safe mechanisms can somewhat mitigate the threat."

In addition, GPS spoofing can interfere with the receivers of other nearby devices. "We are currently developing new technology that can overcome [this]," said Kim.

Safety regulations make commercialization a challenge — in the United States, the Federal Communications Commission stringently monitors radio transmissions. Yet Kim notes that governments are already changing rules in response to the new normal of widespread drone use. In September 2020, the FCC affirmed that drones are permitted to access part of the radio spectrum. 

"Hopefully, after government regulation changes, our new technology could be commercialized," said Kim.

The application for this patent, "Method for Anti-Drone Using GPS Spoofing Signal and System Therefore," was filed on Dec. 23, 2019 to the U.S. Patent and Trademark Office. It was published Feb. 18, 2021 with the application number 16/726049. The earliest priority date was Aug. 12, 2019. The inventors of the pending patent are Yongdae Kim, Juhwan Noh, Yujin Kwon, Hocheol Shin and Dohyun Kim, Korea Advanced Institute of Science and Technology. The assignee is the Korea Advanced Institute of Science and Technology.

Parola Analytics provided technical research for this story.