Researchers at the University of Texas have hijacked a civilian unmanned aerial vehicle (UAV) by spoofing its GPS signals, warning that UAVs could potentially be turned into missiles.

Professor Todd Humphreys and his team were able to take control of a mini helicopter UAV by sending out a GPS signal more powerful than the ones coming down from satellites. They hijacked the drone on June 25, at the request of the US Department of Homeland Security.

Humphreys and his students spent three years and US$1 000 building a spoofer that fed positioning data to the university-owned drone. When the signals from the students matched the signals the drone was receiving from a GPS satellite, the students were able to substitute their data for the satellite's, thus taking complete control of the drone, ABC News reports.

The drone had been preprogrammed with a series of GPS waypoints, but after being hijacked the University of Texas students were able to change its course.

"In 5 or 10 years you have 30 000 drones in the airspace... Each one of these could be a potential missile used against us," Humphreys told Fox News.

"It didn't take expensive equipment, but the software took us four years to develop," Humphreys said. It was possible to hijack the drone because civilian drones are "inherently insecure," he said, as the satellite signals used to guide everything from a GPS system on a cell phone to ships at sea are "unencrypted, open, and unauthenticated."

Military drones are protected by encrypted signals, making it fare more difficult to hijack one, but not impossible. There is speculation that the CIA’s unmanned aerial vehicle recovered by Iran in December last year may have been jammed.