News / Vessels 'go dark' to avoid Houthi attacks, but may still be vulnerable

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Vessels are now resorting to switching off their AIS transponders to conceal their movements and prevent Houthi attacks in the Red Sea – but it could also impact container monitoring.

Playing a critically important role in collision-avoidance, particularly at night or in fog, vessels use other ships’ AIS data as a second line of defence after radar.

Although AIS is legally mandated by the IMO under the International Convention for the Safety of Life at Sea (SOLAS), the organisation does make exceptions for ships under fire.

“If the master believes that the continual operation of AIS might compromise the safety and security of his/her ship, or where security incidents are imminent, the AIS may be switched off,” says IMO Circular A1106(29) para 22.

But in practice, ships often turn off their transponders, but more often than not, this is not because they are liable to be shot at. A notable example in recent years has been the Russian ‘dark fleet’ of tankers carrying sanction-busting oil, evading authorities.

Though the activities of these vessels are secret by design, it is thought that ‘dark fleet’ vessels have been involved in more than 30 accidents, including groundings and fires.

But, as AIS data is available for all to see, Houthi militants gain the opportunity to use the information to stage attacks on vessels and their crews. So by running the Red-Sea gauntlet with AIS turned off, ships can ease the risk of Houthi militants tracking their positions.

However, if Yemenis on shore cannot watch ships passing through the Bab al-Mandab Strait, their drones certainly can, meaning there is still risk to vessels transiting Red Sea.

And a joint statement by shipping industry associations BIMCO, ICS, CLIA, IMCA, Intercargo, Intertanko, IMCA and OCIMF advised that switching off AIS was no guarantee against being attacked.

It advised: “Switching off AIS makes it marginally more difficult to track a ship, but may also hinder the ability of the military to provide support or direct contact.

“Limiting the information in AIS data fields or switching off AIS could make a ship harder to locate, but it is unlikely to ultimately prevent an attack. Limiting AIS data to the mandatory fields and omitting the next port of call could be considered.”

Forwarders, meanwhile, have expressed concern that the lack of AIS could impact the monitoring of boxes.

“Many vessels have switched off their tracking and GPS in the Middle East region to become invisible – container monitoring could become an issue,” said one.