AIS and Security

AIS is a vessel tracking and monitoring system that uses a combination of two, free-to-air communications networks; VHF radio and GPS. Both the position and vessel information is broadcast on the public airwaves and is free to everyone with the capability to receive it. So when it comes to a ship’s AIS security issues, data privacy isn’t an issue. However, this does not mean that it isn’t still vulnerable to external interference and, given its value in traffic management and search and rescue, such interference can end up endangering life.

Threats to AIS system integrity and accuracy relate to the software that underpins the systems, and the radio signals that transmit the data. As such, they fall into three main categories; deception, disruption and detention


Disconnection – Deception comes in a variety of forms. One of these is where a vessel deliberately switches off its AIS transponder so as to conceal its presence or location. This may be because it is involved in illegal activities, or because it wishes to avoid the attention of the media or government agencies. However, the lesson here is, just because your AIS interface suggests that an area of water is empty of vessels, that may not be the case. AIS works best in conjunction with other observational tools including watch keeping and radar.

Falsification – Another form of deception is where a ship maintains an AIS signature but deliberately falsifies the data that it contains, such as the name, type, cargo, MMSI, destination and flag state. Again, this can be for a variety of motives, none of them good. AIS, like any data processing system, is only as good as the information that its users put into it. The general perception is that the vast majority of ship operators enter accurate, if not always complete, data into their AIS transponders.

Malicious weather forecasts: – As AIS can also communicate weather information, deliberately inaccurate weather forecasts have been known to be transmitted so as to attempt to disrupt the operations of commercial rivals.

CPA deception – This involves faking a possible collision with a target ship by falsely triggering a Closest Point of Approach alert. This can prompt the target to change course and thereby possibly prompt it to run into danger.

AIS-SART deception – AIS plays a valuable role in search and rescue (SAR) operations. However, rescue beacons can be activated maliciously to either divert or waste SAR agencies’ resources, or to lure would-be rescuers into dangerous situations.


Timing attacks – Users can program AIS transponders to delay transmission times by simply renewing commands, thus preventing further communications about vessels’ positions and tracks. The opposite can also occur with high frequency updates overloading the available frequencies.

Slot starvation – It is possible for hackers to shut down AIS across a wide area by impersonating maritime authorities to reserve the entire AIS transmission “address space”. This will prevent all AIS transmitters and receivers within that area from communicating with each other.

Frequency hopping – By impersonating maritime authorities, hackers can arbitrarily order AIS transponders to change their operating frequencies on which they operate, thereby compromising their ability to communicate with each other. Hackers can even program target ships to switch frequencies when they reach certain regions.


Hijacking – This is when hackers gain entry to an AIS transponder and modify the information contained within, or else override legitimate transmissions using high-power signals. This can be particularly important where AIS-equipped Aids to Navigation are concerned, and can lead to vessels being placed in danger. Also in maritime areas with political or security sensitivities this can be particularly disruptive.

It should be emphasised that the vast majority of AIS users enjoy an effective, trouble-free experience when it comes to monitoring and tracking vessels. However, no ship’s security system is 100% secure and being aware of possible vulnerabilities is the first step towards avoiding or mitigating them.

About BigOceanData
BigOceanData is a leader in maritime tracking and telemetry, delivering global vessel tracking and monitoring services along with fleet management tools via its sophisticated browser-based interface. Key features of the BigOceanData product include its ability to fuse data from AIS signals and a range of onboard satellite reporting systems so as to both improve position accuracy and reduce data costs. The system also integrates a series of data feeds and management tools that show users not only vessel locations and movements, but situational data such as marine charting, terrestrial mapping, weather and sea-state (current and forecast), and piracy and other security alerts.

For more information contact or call +44 (0) 207 998 3048.