• Russia is accused of using aging tankers to damage undersea cables.
• Analysts say it gives the cover of plausible deniability.
• But it's a method that also comes with risks.

A series of apparent attacks on undersea internet cables show Russia exploiting a Western vulnerability, analysts say.

The incidents in recent months involve aging tankers dragging their anchors and severing undersea cables in the Baltic Sea, prompting outages.

The latest came on Christmas Day, when the tanker Eagle S dragged its anchor for hundreds of miles, damaged the Estlink 2 power line between Finland and Estonia and telecommunications cables.

Officials in Europe say Russia is deliberately using the vessels to target the crucial infrastructure used to transmit internet data and power.

They say the incidents add up to a campaign by Russia to sabotage infrastructure. At least one vessel is said to belong to a "shadow fleet" of ships not directly tied to Russia that it uses to evade oil sanctions.

The means employed, the officials say, are decidedly low-tech: aging tankers dragging their anchors along the seabed for miles, hoping to snag and damage a cable.

One Finnish official on Monday said that Eagle S and its crew were preparing to target more cables before the ship was boarded.

The Baltic and beyond

In November, a Chinese-flagged vessel, the Yi Peng 3, was accused of damaging another cable in the Baltic.

Another Chinese-flagged vessel, the NewnewPolar Bear, damaged subsea communications and gas cables in the Baltic in October 2023 by dragging its anchor. China admitted the vessel was responsible for the damage but said it was an accident, The South China Morning Post reported.

And on January 6, Taiwanese officials said that a Chinese-owned tanker severed cables near its north coast in a parallel incident it blamed on China.

Analysts classify the incidents as likely examples of "grey zone" tactics used by Russia and China to destabilize their rivals while falling short of acts of war.

"Attacks on CUI have become a viable weapon in grey zone warfare," said James Foggo, a retired US Navy admiral, using an abbreviation for Critical Undersea Infrastructure.

"More must be done to preserve CUI in the Baltic and other susceptible regions of the globe," he said in an interview with Business Insider.

Plausible deniability

Using commercial vessels for sabotage comes with risks, but also significant benefits for the attacker.

Henri van Soest, a senior analyst at RAND Europe, told BI that "Russia gets a number of advantages from using its shadow fleet for this purpose. The most important one is deniability and ambiguity: We currently have little insight into the make-up of the shadow fleet."

The ultimate ownership of a vessel can be difficult to establish.

The Eagle S, for instance, is owned by a company registered in the UAE, managed by a firm in Mumbai, and sails under the flag of the Cook Islands.

Analysts assert that Russia is directing the vessel, but there is no verifiable public link.

The Kremlin has itself denied any connection with the Eagle S, and other similar incidents in the Baltic.

The lack of an explicit tie to Russia also allows the ships to navigate freely, drawing less attention from national coast guards than a Russian ship.

A thousand threats, or more

Van Soest also pointed to the size of the fleet — which analysts say could exceed 1,400 vessels. It makes any single ship hard to monitor or counter.

"While currently only a small number of ships are suspected of engaging in sabotage activities, these actions make the entire shadow fleet suspect," said Van Soest.

He said there was a psychological component to the strategy in addition to the actual damage it can cause.

"Any ship that forms part of the shadow fleet could potentially be on a sabotage mission. It also sends the implicit message that Russia could swiftly order a larger number of shadow fleet vessels to start sabotage actions, leading to far greater damage and disruption," he said.

Clumsy strategy

The sabotage playbook comes with risks for Russia.

Pushing too hard with the fleet, Kaushal said, could prompt Western navies to treat it as a hostile entity and try to restrict its movements, reducing its value as a way of overcoming sanctions.

It's also clumsy, said Erin Murphy, deputy director of Chair on India and Emerging Asia Economics at the Center for Strategic and International Studies in Washington, DC.: "Anchors can bounce on the ocean floor and miss cutting the cable entirely, if that was the intent of a ship."

For all that, there is not much Western countries can do that matches the potential scale of the problem.

Limited counterplays

Sweden has said it'll be contributing 3 naval ships to boost NATO patrols in the Baltic to defend against subsea cable sabotage.

And late last year the alliance also deployed divers to test equipment to better defend the cables.

Two further measures proposed by European officials have been to tighten sanctions on vessels in the shadow fleet and boost naval patrols to deter sabotage.

"Increased patrols could help, but there's still the problem in terms of the size of the ocean and waterways," said Murphy.

In short: the sea is just too big to defend.

And Sidharth Kaushal, a research fellow at London's Royal United Services Institute, was skeptical that sanctions would deter the shadow fleet in practice.

Kaushal said that several vessels connected to recent cable-cuttings, including the Yi Peng 3, were not considered to be part of the shadow fleet.

Murphy, the author of a 2024 report on the threat to subsea cables, said nations could pressure the destination ports of suspected shadow fleet vessels to search them or deny them entry.

"This could work for a short time but countries and actors usually find ways to circumvent," she said.

It leaves Western nations with few options beyond chasing shadows.