GNSS spoofing

In global navigation satellite systems (GNSS), a spoofing attack attempts to deceive a GNSS receiver by broadcasting fake GNSS signals, structured to resemble a set of normal GNSS signals, or by rebroadcasting genuine signals captured elsewhere or at a different time. Spoofing attacks are generally hard to detect as adversaries generate counterfeit signals. These spoofed signals are challenging to recognize from legitimate signals, thus confusing ships' calculation of positioning, navigation, and timing (PNT). This means that spoofed signals may be modified in such a way as to cause the receiver to estimate its position to be somewhere other than where it actually is, or to be located where it is but at a different time, as determined by the attacker. One common form of a GNSS spoofing attack, commonly termed a carry-off attack, begins by broadcasting signals synchronized with the genuine signals observed by the target receiver. The power of the counterfeit signals is then gradually increased and drawn away from the genuine signals.

Even though GNSS is one of the most relied upon navigational systems, it has demonstrated critical vulnerabilities towards spoofing attacks. GNSS satellite signals have been shown to be vulnerable due to the signals’ being relatively weak on Earth’s surface. A reliance on GNSS could result in the loss of life, environmental contamination, navigation accidents, and financial costs. However, since 80% of global trade is moved through shipping companies, relying upon GNSS systems for navigation remains unavoidable.

As of 2022, all public-access GNSS systems, such as the US GPS, Russia's GLONASS, China's BeiDou, and Europe's Galileo constellation, are vulnerable to this technique. In order to mitigate some of the vulnerabilities the GNSS systems face concerning spoofing attacks, the use of more than one navigational system at once is recommended. In 2025, Galileo deployed a feature that allows supporting receivers to differentiate between real and forged signals using cryptography.