GPS signal jamming could cause serious, widespread problems

Data and communication networks are among the verticals dependent on GPS timing. A report questions the robustness of the mechanism at the civilian level.

Homeland Security report GPS signal jamming
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Unintentional interference from radios and space can cause problems for the GPS system, as can intentional jamming and spoofing of signals. But communications companies aren't prepared to protect the GPS system from these threats, according to a 2012 Homeland Security report that was recently released under the Freedom of Information Act, as reported by EE Publishing.

The communications sector is "vulnerable to potential long-term GPS disruptions" of a few days or more "that could cause sector-wide service degradations," the report says.


That Global Positioning Systems are vulnerable to interference and disruptions isn't news. However, the apparent lack of preparedness in civilian systems noted by DHS should be an eye-opener.

Space weather can cause problems by disturbing the ionosphere, which affects accuracy—the receiver can't lock on to the satellite signal. Jamming can also interrupt signals, NOAA explains on its website.


What's on the line here? Some people get lost for a few days, or have to dig out a paper map?

It's not that simple. GPS is used for timing as well as location. The quasi-triangulation of the satellites not only tells someone where they are, but it also time-stamps their location.

Each satellite includes an atomic clock. As a ground-located GPS receiver decodes the satellite signals, it also synchronizes the receiver to that clock.

And the tool is used throughout industries. The energy and communications industries use it for timing accuracy. Global banking, for example, also depends on it, as do data networks. Communications networks use it not to itemize a specific call on someone's bill, but to keep all of the phones, base stations, and radios in sync, so they can "share limited radio spectrum more efficiently," explains, the U.S. Government portal about GPS.


Key findings in the now-public DHS report, stored on the nonprofit website, include that although the communications sector is "generally resilient against most short-term disruptions" because it uses good backup timing systems, it isn't protected for long-term outages.

The report's authors also said in 2012 that they think there will be "more frequent localized GPS disruptions" caused by "the availability and increasingly widespread use of low-cost portable GPS receivers or jammers and multi-frequency jammers."

In other words, GPS hacking for sport or financial reward a la cybercrime is on the horizon.

'Hampering' infrastructure

Additionally, "GPS-based applications may experience degradation when GPS disruptions inhibit the distribution or use of GPS timing signals for communications assets, hampering the normal functionality of communications dependent critical infrastructure," the report says.

An example of that could be the energy industry, EE Publishing says in its article. GPS is used heavily in the power industry for tracking "operating conditions on the grid in millisecond intervals," it says.

Low-power hacks

Intentional GPS interruptions aren't new and don't take much signal power from a jammer. Only one picowatt is needed to do it at the GPS antenna, according to Paul Benshoof, of the U.S. Airforce's 746th Test Squadron, writing in an unclassified PowerPoint (PPT) about civilian GPS systems and potential vulnerabilities.

A 100-watt lightbulb "is 1018 (10 to the power of 18) times more powerful than a GPS's satellite signal at the receiver's antenna," Benshoof writes. The jammer could be the size of a soda can, he explained in his presentation.

'Emerging threat'

Jamming of civilian GPS can include spoofing with a counterfeit GPS signal and a widely available signal generator, Benshoof wrote.

Meaconing, which is a delay and re-broadcast, is an "emerging threat," he added.

And there's no off-the-shelf mitigation, at the civilian level, for any of these "disruption mechanisms," he says in the presentation.

The government has other tools, such as strong encryption available to them to secure their systems. The government owns GPS. We just use it, and for free.


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