GPS Jamming

People wanting to stop GPS tracking of their movements are increasingly using devices that scramble tracking systems. "GPS jammers" can be plugged into car cigarette lighters to create a 500 meter zone around their car which interferes with the tracking systems.

GPS Jammer. Image source: www.foxnews.com

According to The Guardian, GPS tracking systems are used to detect stolen vehicles, monitor vehicle use and to stop drivers working overly long shifts. Using the jammers could also impact on plans to introduce pay as you drive insurance schemes or road toll systems. The Guardian cites Prof Charles Curry of Chronos Technology saying that,

"When people use these, it creates a bubble around their vehicle for about 500 metres that jams any GPS receiver or transmitter. ... It stops any tracking system the owner might have put on the car. Usually they will block GSM [mobile phone] signals too that might also be used to send back a location... It means that for anyone trying to track the vehicle, it just vanishes off the map – it's as though it were in an underground car park."

In the UK, it is not illegal to purchase, sell or possess the jammers. It is currently only an offence under the Wireless Telegraphy Act to "knowingly use" such a device to block GPS signals – though according to The Guardian the communications regulator Ofcom is looking to close some of the loopholes. But some see a danger beyond fatigued drivers however, citing the possibility of the devices affecting aircraft navigation systems, and interfering with the GPS systems of drivers in the immediate vicinity, wiping out their signals also.

The need to address the jamming of GPS devices, has also been reiterated by Brad Parkinson, the project leader of the team who originally created the global positioning system in the 1970s. Parkinson discusses the need for higher penalties for GPS jamming offenders and cited Australia's penalties as an appropriate model for other countries to adopt. He cites an incident where during testing at Newark airport of GPS technology for the blind landing of planes, researchers found that the signal would periodically get jammed at the same time each day. The cause was pinpointed to a truck driver who was trying to jam the GPS on his truck, but the reach of the device to interrupt with the airport signals suggests the potential seriousness of jamming.

In May 2012, the North Koreans used much more powerful jammers to scramble GPS signals near two of South Korea's major airports. The Russian built devices are claimed to be able to affect systems as far as 100km away.

The Australian Communications and Media Authority (ACMA) has intercepted and destroyed nearly 100 illegal signal jammers that interfere with GPS and mobile devices. According to the Sydney Morning Herald (SMH), the jammers were intercepted through the mail between November 2011 and June 2012.

The jammers are illegal in Australia and the possession or supply of the devices can be met with heavy fines and possible imprisonment of two years. Body corporate's can receive up to $225 000 for the offence, while causing interference to radio communications used by emergency services can attract a fine of up to $850 000 or a five year prison sentence.

The SMH states that the ACMA believes most jammers are typically used by those who want to stop mobile phone calls from being made or received in a certain vicinity.

"Others just use them to cause a nuisance. In one example several years ago, the regulator found an imam at a Western Sydney mosque using one during prayers to ensure there was silence. In another, a company installed one in its boardroom after getting advice from a security expert."

There has been a decrease in the number of jammers seized by authorities. According to Mark Loney, executive manager, ACMA's operations and services branch,

"My sense is that the rate of intercepts to the mail stream is falling," he said. "That could be a good sign and that there's less people buying them. Or it could mean that they are coming in and are not being picked up in the mail stream. We don't have perfect knowledge about this but the fact that we're seeing less is encouraging."

The NSW Department of Corrective Services is the only organisation approved within Australia to be granted an exemption. They are currently trialing the jammers at Lithgow jail after an inmate smuggled in a mobile phone with which to control drug operations on the outside.

Jamming GPS becomes problematic when the amount of infrastructure and systems that rely on global navigation satellite systems (GNSS) for deriving position, navigation and timing data (PNT), of which GPS is the most widely used, are considered. The services to which the technology is applied ranges from car navigation, data networks, financial systems, shipping and air transport systems, agriculture, railways, emergency services, and safety of life applications. According to the Royal Academy of Engineering (RAE), many of these systems have GPS as a shared dependency, so a loss of signal could cause the simultaneous failure of many services that are probably expected to be independent of each other.

Furthermore, our reliance on GPS systems continues often without a non-GNSS back-up, or inadequate back-up if contingency plans have been put in place. Therefore, any disruption to the signal can result in a range of consequences dependent on the application. The RAE notes that,

disruptive interference can occur unintentionally and, worse still, deliberate interference is a real and growing possibility. As opportunities arise for criminals to make money, avoid costs or avoid detection, it is known that significant effort will be directed towards attacking GNSS based systems. The banking infrastructure has already seen such an increase in high-tech attacks and now devotes considerable time and expense to countermeasures. Potential and already known mechanisms for deliberate interference include: 

• Jamming GNSS based vehicle tracking devices to prevent a supervisor’s knowledge of a driver’s movements, or avoiding road user charging.
• Rebroadcasting (‘meaconing’) a GNSS signal maliciously, accidentally or to improve reception but causing misreporting of a position.
• Spoofing GNSS signals to create a controllable misreporting of position, for example to deceive tracking devices.

As the use of GNSS for revenue raising purposes increases through road user charging or vehicle tracking, the prevalence of cheap jamming devices will increase. Because the signal received at ground level from the GNSS satellites is weak – it may be as low as -160dBW (1 x 10–16W) – jamming over a small area is easily achieved and it is known that dedicated kit is already readily available for purchase over the internet even though use of that equipment in the UK is illegal. In the United States, monitoring for GPS signal anomalies is routine and the occurrence of jamming incidents, both deliberate and accidental is growing. In the UK, the Technology Strategy Board is supporting a project to establish a service to verify the extent to which GNSS signals can be trusted by users.

Fox News also recently reported on research at the University of Texas which demonstrated the vulnerability of the GPS system. Using a laptop, a small antenna and an electronic GPS “spoofer” built for $3,000, GPS expert Todd Humphreys and his team were able to gain control of a sophisticated navigation system on board a super yacht involved in the research. The team were able to use counterfeit radio signals to steer the vessel and take it off course, while on board, the ship's GPS system indicated the ship was still on course. The research team suggested that such GPS "spoofing" could cause major havoc in maritime contexts and could be also used to interfere with the systems on commercial aircraft. This has obvious implications for security considering the system's vulnerability to be hacked.

Responding to this requires both awareness and policy changes to increase resilience and robustness of GNSS systems. Australian company, Locata has invented what they claim to be the World's first local GPS system, "Locatalite", which "plugs" holes in GPS and offers independent positions, navigation and time capability as well as local back-up for GPS.  The RAE offers a series of recommendations to address the GNSS resilience issues and suggests,

The provision of a widely available PNT service as an alternative to GNSS is an essential part of the national infrastructure. It should be cost effective to incorporate in civil GNSS receivers and free to use. Ideally it should provide additional benefits, such as availability inside buildings and in GNSS blindspots.

These solutions address the infrastructure and technological side of GPS disruption, but perhaps responses should also be directed to understanding the reasons for why people use jammers. Criminal reason's aside, there are issues of increasing surveillance of worker's and the associated discomfort and mistrust encouraged by such tracking; also the need for engaging in activities without the interference of mobile phones, such as in cinemas, and as noted in the Sydney mosque example. Perhaps in these circumstances, focus should not be solely on technological solutions but on social solutions too, and working towards resolving the issues which entice people to use the jammers.