Researchers Demonstrate How to Spoof GPS Devices
Tuesday, September 30th, 2008
With millions of GPS-based navigation devices on the road today, it is time someone considered the question: What if there’s an attack on the GPS network itself?
Researchers at Virginia Tech and Cornell University spent more than a year building equipment that can transmit fake GPS signals capable of fooling receivers.
“GPS is woven into our technology infrastructure, just like the power grid or the water system,” said Paul Kintner, electrical and computer engineering professor and director of the Cornell GPS Laboratory in a statement. “If it were attacked, there would be a serious impact.”
GPS is a U.S. government-built navigation system of more than 30 satellites circling earth twice a day in specific orbits. The satellites transmit signals to receivers on land, sea and in air. Based on the signals received from the satellites, devices are able to triangulate their exact positions on the globe. But if those satellite signals were wrong — or were spoofed — a GPS device might come up with the wrong location based on the signals it was receiving.
The researchers started by programming a briefcase-size GPS receiver used in the research of the uppermost part of the Earth’s atmosphere, known as ionospheric research, to send out fake signals. The phony receiver was placed in the proximity of a navigation device, where it anticipated the signal being transmitted from the GPS satellite. Almost instantly, the reprogrammed receiver sent out a false signal that the GPS-based navigation device took for the real thing.
The experiments to show the vulnerability of GPS receivers to spoofing could help devise methods to guard against such attacks, says Brent Ledvina, an assistant professor of electrical and computer engineering at Virginia Tech, and will be detailed in a research paper to be released Thursday.
“It’s almost like someone nearby is spoofing your favorite radio station by transmitting at the same frequency but higher power fooling your receiver into believing it is getting the right station,” says Ledvina.
The idea of GPS receiver spoofing has already been considered by federal authorities. In a December 2003 report, the Department of Homeland Security detailed seven countermeasures including monitoring the absolute and relative GPS signal strength, monitoring the satellite identification codes and the number of signals received and checking the time intervals between the received signals to guard against spoofs.
Still those fall short and would not have successfully fended off the signals produced by a reprogrammed receiver, said the researchers.
Instead they have suggested a few countermeasures that involve both hardware and software changes. “We have two patent applications which include a software algorithm to help make changes to how receivers react to signals,” says Ledvina.
The other patent is around the spoofer tool used, he says. “The idea is to help government and other companies use it to potentially make better receivers,” says Ledvina.
Photo: NASA
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