What is GNSS/GPS spoofing?

Not getting a GNSS signal? The reasons why might not be as innocent as you think. In the world of GNSS there are many natural reasons for errors and outages that occur, preventing you from getting an accurate position. But what about the man-made causes? In previous posts, we’ve talked about jamming as a way to block GNSS signals. Now, let’s take a look at spoofing.

By its definition, spoofing is the transmission of fake signals designed to trick a GNSS receiver into computing an incorrect position. The radio frequency spectrum is split into designated uses with fixed GNSS signal bands with known frequencies, making them susceptible to spoofers emitting signals within the same frequency range.

Disruptions to GNSS signals can have severe consequences for industries that rely on accurate positioning for critical operations, including aviation, marine, and defense . While other errors and interference may be generated from innocuous sources, spoofing is always an intentional attack.

How is a GNSS receiver spoofed?

Typically, step one in spoofing a GNSS receiver is to jam it by broadcasting a signal in the GNSS band at such intensity that it overwhelms the receiver. When jammed, a receiver cannot register the targeted GNSS signals to provide positioning, navigation and timing (PNT) data.

Step two is providing a false satellite signal that is either created by a signal generator or is a rebroadcast of a real recorded GNSS signal, called meaconing. In the spoofed signal, the message is changed so that the receiver will calculate an incorrect position or time. As the spoofer increases the power it’s transmitting the spoofed signal at, it becomes stronger than the true signal so that it becomes the only signal the jammed receiver can identify to use. Users acquire and then start tracking the false signal. The complexity of a spoofing attempt increases if the attacker tries to simultaneously spoof more than one GNSS frequency across constellations.

How do I know if I’m being spoofed?

The first indicator that you are being spoofed is that something in your positioning output seems off. For example, you may look like you are going in circles when you aren’t, or there might be drastic and sudden changes to your last known position or speed. Identifying and detecting interference is the first step towards detecting a spoofing attack, but you would have to be watching for it to know it’s happening. Our webinar featuring an introduction to jamming, spoofing and interference helps provide a baseline of knowledge for users to recognise when there’s a problem. Once you can identify jamming and spoofing, then technology can come to your defense. 

Learn more about how spoofing attacks are detected in our Velocity article Try to spoof us. But fool us? Not a chance.

How can I protect against spoofing?

NovAtel’s GNSS Resilience and Integrity Technology (GRIT) is a firmware suite developed to expand situational awareness and interference mitigation tools across applications and environments to protect against GNSS interference. Under the GRIT portfolio on any OEM7 receiver, the user can see clearly whether a signal is jammed or spoofed and mitigate it before it impacts the final PNT solution.

Our world is becoming increasingly reliant on GNSS. Ensuring the resilience and integrity of GNSS positioning is key to not only smooth operations, but also the safety of people and infrastructure. Learn more about NovAtel’s Interference Mitigation tools.

If you are interested in learning more about jamming and spoofing, please download our white paper Spoofed or jammed? Busting the myths of GNSS interference and mitigation.