satellite network (Andrey VP/

Protecting the ‘invisible utility’ of GPS

When it comes to threats on critical infrastructure, the most disruptive might be any interruption of GPS or position, navigation and timing (PNT) services because all 16 sectors – not to mention space and military applications – rely on those timing and navigation services.

The Department of Transportation is the lead civilian agency working with the Defense Department to modernize GPS and develop a backup system in case satellites quit working or adversaries jam or spoof signals – especially those around the timing data it provides. 

The nation must be prepared not just for disruption of GPS signals, but for the cascading effects that disruption would have across sectors, said DOT Director for Positioning, Navigation, and Timing and Spectrum Management Karen Van Dyke.

Speaking at the 2021 Sea Air Space conference, Van Dyke said GPS synchronization provides an “invisible utility” and warned of adversaries not only jamming GPS signals, but also spoofing GPS measurements and data.

“In measurement spoofing, once the signal goes away, the receiver recovers. With data spoofing, the effects could be long-lasting and the receiver may never recover,” she said.

To ensure the security and reliability of GPS, Van Dyke said her office “really embrace[s] what we refer to as the PTA principal: protect, toughen and augment.” That means monitoring to detect interference and service disruptions.

Van Dyke said her office is also focusing “on authentication -- ensuring that the signal that you're seeing if you’re using GPS or any other PMT technology is truly coming from intended source.”

To help protect PNT services, agencies and businesses should take a step back and think about their operational requirements and what technologies can meet those needs.

That may mean “not automatically integrating a GPS receiver because it's low cost and it's available everywhere, but thinking through what vulnerabilities might be introduced into your network because of limitations we've identified with GPS,” she said.

Another potential vulnerability lies in spectrum management.

“GPS relies on radio frequency spectrum that absolutely must be protected from harmful interference,” Van Dyke said. “We’re doing everything we can to protect it from authorized sources of interference ... but we can’t control unauthorized sources of interference” that jam and spoof signals.

“Until we can move to a world where we really are resilient, we have to understand our vulnerabilities and the amount of risk and disruption we can tolerate,” she said.

“And if you can't live with that answer, what are you going to do about it?”

About the Author

Susan Miller is executive editor at GCN.

Over a career spent in tech media, Miller has worked in editorial, print production and online, starting on the copy desk at IDG’s ComputerWorld, moving to print production for Federal Computer Week and later helping launch websites and email newsletter delivery for FCW. After a turn at Virginia’s Center for Innovative Technology, where she worked to promote technology-based economic development, she rejoined what was to become 1105 Media in 2004, eventually managing content and production for all the company's government-focused websites. Miller shifted back to editorial in 2012, when she began working with GCN.

Miller has a BA and MA from West Chester University and did Ph.D. work in English at the University of Delaware.

Connect with Susan at [email protected] or @sjaymiller.


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