GPS 'spoofing' could threaten national security

Tag : GPS system

The easiest way to mess with a GPS device is simply to jam it, orcreate a false GPS signal that overpowers the real GPS signal. Inthis case, the victim would know about the sabotage right away;often the GPS receiver simply doesn't work.
The second, more sinister, method is called spoofing. In spoofing,the intended target doesn't know that the signal received from aGPS unit is wrong: A spoofer creates a false GPS signal that passesas a real GPS signal, and an incorrect time or location appears onthe intended receiver.
"It looks exactly like a real GPS signal," said Ledvina."Everything looks completely normal, but the spoofer is controllingyour position in time and space."
Being a couple microseconds off of the real time might not soundlike a big deal to the average consumer with a GPS car navigationsystem, but GPS has spread far beyond what its creators envisionedin the 1970s.
Being even 10 microseconds off could cause power generators, someof which use GPS signals to sync electrical grids to powerstations, to explode, said Ledvina. Air traffic controllers use GPSto help avoid plane collisions. Banks time-stamp financialtransactions using GPS. Police attach GPS receivers to criminals tomonitor their activities.
At its worst, successfully spoofing a GPS receiver could mean planecrashes and exploding generators. A more likely scenario, said PaulKintner of Cornell University, is less disastrous but still illicit-- people could falsify their geographic or chronological positionto avoid house arrest or authorities, for instance.
"Apparently fisherman are required to carry a GPS monitoring unitand already have made crude attempts at spoofing," said Kintner."There are likely more examples of where people do not want to betracked that would gladly pay for a spoofer."
The good news is that, for now, it is still pretty hard to create aspoofer. Some of the study authors have been working on GPStechnology for more than 15 years now. Kintner estimates it costthem over $1 million to build their spoofer (includingmanufacturing costs). Ledvina says the hardware alone was about$1,000.
The spoofer itself was the size of a briefcase and was plugged intothe wall. The scientists also connected the spoofer to a GPSreceiver with a cable instead of broadcasting the signal, whichwould have violated FCC regulations.
If they had broadcast the signal it would only go a few meters,which means the spoofer and the intended receiver would have to bephysically close. Eventually the size of a spoofer could decreaseto about the size of a pack of cigarettes.
That said, it only took two part-time students about a week of workeach to build the spoofer. The cost of hardware and the expertisenecessary to build the next spoofer will drop quickly as well, asLedvina illustrates.
"Ten years ago it would have taken a grad student a few weeks tojam a GPS receiver," said Ledvina. "Now Virginia Tech probably has100 students who, with the right equipment, could build a jammer inabout ten minutes." Ledvina expects a similar trend to followspoofing.
Spoofing is not a new concern.
In 2001, the U.S. Department of Transportation released a report onGPS that laid out six countermeasures to deter spoofing, such asadding additional, non-GPS instrumentation, or keeping humans incharge of decision instead of leaving them up to computers. Butsuch measures can be expensive, and they don't necessarily solvethe problem.
The Cornell and VT team has successfully found a way around five ofthe six countermeasures, and are currently working to crack thelast one.
The only GPS systems that can't be spoofed are military systemsused by some soldiers and GPS guided "smart-bombs," says RichardLangley, a GPS researcher at the University of New Brunswick whoreviewed the Cornell and Virginia Tech research.
"The military GPS signals are protected against spoofing by using asecret encryption, so that only receivers with that encryptiontechnology can access the signal," said Langley. "There is no suchprotection for civilian GPS use."