On the occasion of the International Day of the Seafarer on 25 June, a total of 14 maritime organizations sent a formal letter to the US Coast Guard Commandant Karl Schultz, requesting the issue of 'deliberate interference' with America’s Global Positioning System (GPS) and other Global Navigation Satellite Systems (GNSS) signals to be resolved.

This comes following a series of GPS interference incidents endangering maritime operations of US vessels.

A recent report by C4ADS highlighted that Russian GNSS attacks are emerging as a disruptive and strategic threat.

As reports of GNSS manipulation are on the rise, a new paper by Nettitude, a Lloyd's Register company, gives a summary of how GPS operates, what features make it susceptible to attack and what is the impact in the marine and offshore industries.


GPS cyber threats

-Jamming attacks deny access to a radio resource by broadcasting a far stronger signal which ‘swamps’ local receivers and prevents them from being able to decode the legitimate signal.

Due to the high-orbit and corresponding weak radio signal at ground-level, GNSS systems are particularly susceptible to jamming attacks because even a low-power signal will deny access over a large area.

-Spoofing works by a local transmitter generating a set of PRN codes and other GNSS information (such as the navigation message), and broadcasting them to the target receiver at a higher power than the legitimate satellites. Since the signals are transmitted at a higher power the receiver will ‘see’ them in preference to the real signal.

By carefully controlling the PRN codes and when they are transmitted the spoofer can trick the receiver into calculating an inaccurate fix and time.


Impact in the marine and offshore industry

In 2017, the UK Government commissioned a study into the impact on the UK economy if GNSS systems were to be disrupted for just five days with the cost to the maritime sector being estimated at £1.1 billion.

This was predominantly due to disruption at ports due to container cranes reliance on positioning information leading to difficulties loading and unloading containers.

More widely however, GNSS disruption would also prevent systems the maritime industry uses (such as telecommunications networks) operating effectively and the complex network of dependencies means it is likely that unforeseen effects would take place.



In regard to the above, Nettitude advises owners to assess use of GNSS location fixes and ensure they have considered the risk of that being interfered with. This might include:

  1. Understanding likely exposure to GNSS interference based on geography and sector.
  2. Discuss available mitigations with device manufacturers, both in software and hardware.
  3. Understand the way that systems behave if GNSS systems are unavailable.
  4. Ensure staff are trained in how to react if they encounter GNSS system issues and know who to report them to.