Undersea cables are vulnerable to sabotage – but this takes skill and specialist equipment

Countries have come to rely on a network of cables and pipes under the sea for their energy and communications. So it has been worrying to read headlines about communications cables being cut and, in one case, an undersea gas pipeline being blown up..

Critical undersea infrastructure (CUI) as these connections are known, supports about US$9 trillion (£6.6 trillion) worth of trade per day. A coordinated attack on this network could undoubtedly have devastating consequences.

But, as a former submarine commander who researches maritime security, I believe that attacking and disrupting the network is not as easy as some reports might make it appear. Deliberately snagging a pipeline with a dragging anchor in relatively shallow waters can cause a lot of damage, but it is fairly indiscriminate trick with a shelf life, since the damage can be repaired, and deniability becomes increasingly difficult.

Targeting the cable networks in deeper waters require more sophisticated methods, which are much more challenging to carry out.

A hostile state wishing to attack this network first needs to locate the cables they wish to target. The majority of the newer commercial cables are very clearly charted, but their positions are not exact.

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Cables and pipelines, even the heaviest ones, will drift somewhat as they are laid, and the deeper the water they sit in, the greater the distance they may drift.

Those newer cables are often buried in a shallow trench to protect them, which makes locating and accessing them more challenging. Older cables were laid in slightly less exact navigational times, some before the GPS network was available for civilian use. They are not in pristine or predictable patterns.

The positions of cables used by the military are generally not advertised at all, for reasons of security. Locating the target cable requires a detailed understanding of the topography and features of the seabed. That sort of picture can only be built up by survey and reconnaissance.

Accurately surveying the seabed takes time and significant effort. And to get certainty of the picture, the survey or reconnaissance operation needs to be conducted in overlapping rows. This is painstaking work which is conditional upon the state of the sea.

Specialist equipment

Identifying a cable against the seabed or in the trench in which it lies requires a sonar resolution of something in the order of one or two metres, requiring specialist equipment.

In 2024, several submarine telecommunications cables were disrupted in the Baltic Sea. Although there had been suspicions about ships dragging their anchors to damage the cables, authorities were not able to confirm this. The damage has not been conclusively attributed to a third party.

There have been fears about “hybrid warfare”: deniable actions taken another nation that are enough to cause disruption, but are not enough to be an attributable act of war.

In 2017, the UK chief of the defence staff said that Russia posed a threat to undersea cables. Russia has spent considerable money, time and effort in developing the platforms and capabilities that could target undersea infrastructure, if the country so wished.

An organisation called the Main Directorate of Deep-Sea Research (GUGI) operates deep-diving nuclear submarines, as well as a survey ship that is equipped with a deep diving submersible capable of operating at 6,000 metres.

Russian navy

The Russian navy also operates survey vessels such as the Akademik Vladimirsky. The precise sensors that the ship is equipped with are unknown – but in a 2012 research expedition to the South Pole it deployed a proton magnetometer, which can be used to discover metallic objects on the seabed such as pipelines.

However, there is no suggestion that these survey vessels have been involved in disrupting undersea infrastructure. Nevertheless, operations by such vessels do not go unobserved by the west. Indicators and warnings of their deployments can be gained from imagery, and western submarines are capable of tracking and observing their patrols.

The threat posed to Europe’s critical undersea infrastructure is real, and the consequences of a successful attack could be catastrophic. But this is a difficult business in a very challenging environment.

The most acute threat is in the littoral (shore zone), where cables make landfall and in the shallows around those landing places. Protecting these chokepoints should be a top priority.

That, in turn, requires adequate numbers of attack submarines capable of monitoring and, if necessary, deterring or disrupting hostile activity. Vigilance, investment, and realism – not alarmism – will be the foundation of a credible undersea defence.

John Aitken does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.