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Under the sea, a shadowy hybrid war is being fought. In November, a Chinese-owned freight vessel was suspected of severing two fibre-optic cables under the Baltic from Germany to Finland and Sweden to Lithuania. A month later, Finnish coastguards seized a tanker carrying Russian gasoline that allegedly cut a subsea power connector between Finland and Estonia, and damaged four telecoms lines. Early this month, Taiwan asked South Korea to help it investigate a Chinese-owned ship suspected of damaging an internet cable off its northern coast. Global democracies are having to wake up fast to the dangers of sabotage of vital subsea infrastructure carrying energy or data — including trillions of dollars of daily financial transactions.
China blamed a previous incident in October 2023 when a Hong Kong-registered vessel cut a natural gas pipeline also between Finland and Estonia on an “accident caused by a storm”. But Finnish authorities say there is “close to zero” chance that this and the two recent apparent acts of sabotage in the Baltic were all accidents or bad seamanship. They found that the Eagle S, the tanker in December’s incident, dragged its anchor for nearly 100km through the Gulf of Finland.
Though Finland has not publicly accused Russia, many see Moscow’s hand behind these episodes, potentially using ships owned by China and others. The incidents have raised alerts that the “shadow fleet” of ageing, poorly maintained and underinsured tankers being used to evade western sanctions and carry Russian oil to Asian customers — which already pose significant environmental risks — may be being deployed for more threatening activities too.
The vulnerability of subsea installations, however, was first exposed by explosions in 2022 that blew up the two Nord Stream gas pipelines connecting Russia to Germany. German authorities last year blamed Ukraine, though the investigation continues. Taiwan’s experience, moreover, suggests sabotage risks are far from just a European phenomenon. Globally, the vulnerabilities are acute. Cables carry about 98 per cent of internet traffic, including $10tn in daily transactions on platforms such as Swift that drive global markets. Energy networks are ever more interconnected.
Western militaries are starting to react. At a meeting in Helsinki on Tuesday, Nato launched a mission called Baltic Sentry to protect subsea infrastructure in the region involving frigates, maritime patrol aircraft and naval drones. More satellite tracking of ships is needed to identify suspicious behaviour, since shadow fleet vessels often turn off the transponders that signal their position.
The US and allies also need to step up efforts to curb the shadow fleet. Navies and coast guards have been wary of stopping vessels that under international law enjoy the right of “innocent passage” through other countries’ waters, for fear of triggering tit-for-tat retaliation or diplomatic or military incidents. That right is lost if ships are engaged in nefarious acts, but knowing that without boarding can be tricky. The Finnish authorities’ move to seize the Eagle S and launch an investigation into suspected gross sabotage, however, suggests a welcome readiness to act more robustly against suspicious vessels.
The often private-sector operators of subsea networks have a role, too, in installing more security measures, and building more redundancy into systems to enable rapid rerouting. Billions of dollars of investment in back-up cables, and in expanding the existing fleet of repair ships, is needed to speed up response times. But in a world of increasing tensions, this may be a lot cheaper than dealing with the consequences of any concerted attack.
