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GNSS Electronic Interference in the Mediterranean

The NATO Shipping Centre (NSC) continues to receive and process reports provided by merchant mariners related to GNSS electronic interference, particularly in the Mediterranean Sea. All data is treated as confidential, with aggregate data improving the maritime situational awareness (MSA) picture for all maritime traffic. The NSC has issued an August 2021 Threat to Commercial Shipping in the Mediterranean and Electronic Interference Assessment on 26 August 2021. This article uses the NSC`s analysis of 2020 and 2021 data through 07 September 2021 to identify trends and "hot spots" relative to mariner observations of loss of Global Navigational Satellite System (GNSS) signal and interference. The two primary forms of GNSS interference are spoofing and jamming.

GNSS Spoofing

GNSS spoofing simulates a GNSS signal, manipulating positioning, navigational and timing (PNT) data, forcing the receiver to display this false data. Spoofing can be an overt or covert operation. An example of spoofing is a carry-off attack, where a false signal is broadcasted synchronously with a genuine signal, with the power of the false signal gradually increasing over time, so that the vessel's GNSS receiver tracks the false signal, allowing manipulation of PNT data. Another example is meaconing, which is the interception and re-broadcasting of a GNSS signal.

GNSS Jamming

The second primary form of GNNS interference is jamming, which is an effort to restrict use of GNSS. It is caused by interference to the signals at GNSS frequencies, preventing the GNSS receiver from detecting and processing the authentic signal due to being overwhelmed by the strength of the jamming device, which exceeds that of the weaker GNSS signal receiver.


Electronic interference reports received by the NATO Shipping Centre did not pose any serious impact to shipping. Interruptions to GNSS signals and dependent systems, such as AIS and ECDIS, were temporary. Figure 1 provides an aggregated view of areas where mariners have observed electronic interference. Mariners should heighten their vigilance related to the accuracy and availability of PNT data when transiting the areas marked in red.

_nato4 The NATO Shipping Centre continues to appreciate and request that merchant mariners reports any suspicious activity observed within the Mediterranean Sea, including GNSS interference.

Story by NSC at MARCOM

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