GNSS jamming and spoofing explained
An AMS-IX Story
AMS-IX
Most people only associate GPS with navigation. But Global Navigation Satellite Systems such as GPS, Galileo and GLONASS support much more than helping us get from one place to another. They provide the positioning and timing information that underpin telecommunications networks, financial transactions, logistics operations and many other digital services.
For many organisations, GNSS has become a critical dependency. Yet the signals that make it all possible come with a natural limitation. By the time they travel thousands of kilometres from satellites in orbit to receivers on Earth, they are relatively weak. Some experts compare them to a whisper from space. That whisper contains enough information to determine a precise location and provide highly accurate timing, but it can also be disrupted or manipulated.
This vulnerability creates an opportunity for interference. The two most common forms are jamming and spoofing. Although these terms are often used together, they describe very differentthreats and can have very different consequences.
When the signal disappears
Jamming is the intentional disruption of GNSS signals. Imagine trying to hear someone speaking quietly in a crowded room. If the environment remains relatively quiet, the conversation is clear. But if someone suddenly starts shouting, the original voice becomes impossible to hear.
The same principle applies to GNSS. A jammer transmits a stronger radio signal on the same frequency used by GNSS satellites. Because the legitimate signal is already weak, the receiver can no longer distinguish it from the interference and lose access to the satellite signal altogether.
When this happens, positioning and timing information become unavailable. Asset tracking systems may stop working; telecommunications networks may experience synchronization issues, and services that rely on accurate timing may need to switch to alternative sources.
While the impact of jamming can be significant, it is usually easy to identify because receivers lose access to the signal completely. Organisations know something is wrong, even if they do not immediately know the cause.
When the signal starts lying
Spoofing takes a different approach. Rather than blocking the real signal, attackers create fake GNSS signals that appear legitimate to the receiver.
Imagine that someone imitates the voice of the person you trust and starts giving you different instructions. You can still hear a voice, but the information is no longer coming from the right source.
A spoofing attack works the same way. The receiver continues to receive what appears to be a valid GNSS signal, often without generating any warning. Instead of losing positioning or timing information, the receiver begins calculating the wrong position or time.
This makes spoofing particularly concerning because systems may continue operating normally while relying on inaccurate data. Locations can appear correct when they are not, and timing information can drift from reality. Decisions continue to be made, but they are based on information that is no longer accurate. One of the most cited examples of this risk is in aviation where a spoofed signal can cause an aircraft to believe it is exactly where it should be, while it is, in reality, somewhere else entirely.
Understanding the difference
The distinction between jamming and spoofing is simple. Jamming prevents receivers from obtaining GNSS information, while spoofing feeds receivers' false information that appears genuine.
Both exploit the same weakness: GNSS signals are relatively weak by the time they reach Earth. However, the impact is very different. One creates disruption by making positioning and timing information unavailable. The other introduces incorrect information into systems that continue to operate normally.
As dependence on satellite-based positioning and timing continues to grow, being aware of these vulnerabilities isbecoming increasingly important. GNSS is no longer just a navigation technology. It has become a critical part of the infrastructure that supports the digital economy.
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