GPS jamming

GPS devices are big business - one 2011 industry analysis estimated the global market for portable navigation would reach $75 billion by 2013.

These days, they're everywhere – from the smartphone in your pocket to the satnav in your car, from airplanes to ship navigation systems. But, one major drawback of GPS is that the distant, low-power radio waves that provide data to all these devices can be blocked easily by more powerful jamming signals.

However, no-one really knows how often this happens.

So, in an experiment that started in January last year, researchers in the UK have been trying to discover the level of risk posed by GPS jamming. They placed 20 monitoring devices at roadside locations across the country, from city streets and motorways to quiet country roads.

Last month, the conclusions of the project, known as Sentinel, were presented to a conference at the National Physical Laboratory in London.

Hundreds of occurances daily

“What we see is that probes near main roads get a number of hits, sometimes several hits a day,” said Bob Cockshott, who organized the meeting.

“Probes in quiet locations, away from main roads, don’t see anything. So we believe the circumstantial evidence is very strong: we’re seeing vehicle-borne jammers in use. There are probes here in London, but because this is very much at an experimental stage, the location is not yet public.”

At one site, the probes detected 67 jamming incidents over a six-month period, and the company which led the research, Chronos Technology, estimates that there are between 50 and 450 occurrences each day across the UK.

So who is carrying out this jamming, and why?

“The threats that we’re seeing now are people trying to defeat trackers, so for example a van driver with a tracking device on the van may want the disguise the fact that he’s moonlighting in the van at lunchtime,” Cockshott told DW.

“We have seen that. They’re also more serious threats, such as very powerful jammers that are used to defeat GPS tracking systems, for example on trucks carrying high value goods.”

English Channel a possible chokepoint

His assertions are backed up by some evidence. A couple of years ago, a gang was caught using GPS jammers and mobile phone jammers in order to hijack expensive vehicles, and to prevent the drivers from calling for help.

But it’s not only jamming threats that were highlighted by the London conference.

“The guy with the spoofer can cause the receiver, the GPS satnav, to show wherever he wants it to show,” explained David Last, a GPS consultant and professor emeritus at the University of Bangor, Wales. “So he can make a vehicle that is being tracked appear to continue along its planned route, for example, when it’s being stopped and hijacked.”

However, there’s never been a recorded civil spoofing attack. And the kind of incidents that Sentinel detected point to some pretty low level criminality - not the kind of mass disruption that could threaten lives or national security.

“So it would certainly be perfectly possible to put a jammer on the cliffs overlooking the English Channel and take GPS out from every one of the vessels – there are five hundred a day that come though – is the most busy choke point in the world,” Last added.

Jamming on the cheap

But it’s not just about interfering with geographic location data. Experts warn that the highly accurate GPS timing used by modern telecoms and global stock markets could also be sabotaged.

Given the risks to vital infrastructure, some are calling for the law to be tightened up in the UK. It’s already illegal to sell or use a jammer here, but it is still legal to own or buy one.

In fact, the regulatory body for communications, Ofcom, has become stricter in recent years, causing some – like Steve Roberts, from the website OSS Technologies - to take jammers off his virtual shelves.

“They’re clamping down on anything like that, anything to do with the communications frequency really,” Roberts told DW. “So we didn’t want to get on their backs. And also there’s a moral aspect to selling jammers, and we couldn’t see a reason, a valid reason for selling them.”

But Roberts is the exception. Handheld jammers are easily available over the net for under 50 euros ($65), and manufacturers – typically in China and the Far East – are making cheaper, smaller versions all the time.

“The statistics we gather should be applicable all over the world. I think what we’re seeing in the UK is just a snapshot. There’s certainly no reason to think this is not happening all over the world,” Cockshott added.

But this study isn’t the final word on GPS jamming and spoofing - there are plans under way for a larger scale project to follow Sentinel here in the UK, and other countries are getting in on the act too - most notably in the United States.

Author: Robin Powell, London
Editor: Cyrus Farivar