Undersea cables are the backbone of globalization in the internet era — running across the ocean and sea floors to link nations and continents on different sides of the world.
A 2021 report by Total Telecom puts their number at close to 500, with a combined length of around 1.3 million kilometers (808,000 miles). The numbers have only grown since.
“All of global data exchange flows through these cables,” said Johannes Peters, the head of the Center for Maritime Strategy and Security at the Christian Albrechts University in Kiel.
“The internet, payment orders, any kind of information you can think of, any kind of spoken communication, it runs almost exclusively through these cables,” Peters told DW. “On a global level, we are dependent on them.”
But these communication networks are increasingly seen as targets for potential sabotage.
The danger has been made plain by an ongoing series of incidents in the Baltic Sea. A study by the Washington University in Seattle found some 10 cables have been severed since 2022, including seven between November 2024 and January 2025, with additional incidents reported this summer.
Russia was repeatedly named as a possible offender, based on recorded ship movements or anchor trails. But Moscow’s responsibility has not been proven beyond all doubt, and the same goes for the claims that the damage was done on purpose. It is also possible that the cables were damaged by accident or due to negligence.
China is also suspected of damaging some of the data cables in the Baltic Sea and near Taiwan. Last November, Sweden urged China to take part in a probe related to one such incident.
Trouble brewing in the Pacific?
Asian nations are also vulnerable to undersea cable damage. US allies Japan and South Korea, as well as Taiwan — a self-ruled island which Beijing sees as Chinese territory — are connected to the US via cables running across the bottom of the Pacific Ocean. Their leaders fear that these underwater cables could be targeted in case of a conflict with China.
According to a report by the Center for Strategic and International Studies (CSIS) in Washington, China has already developed a ship that can cut cables lying as deep as 4,000 meters (over 13,100 feet) under the surface.
US officials are also issuing similar warnings. The US-China Economic and Security Review Commission, tasked with briefing the US Congress, recently reported that China had “increasingly engaged in undersea cable-cutting activities as a gray zone pressure tactic, and there is mounting evidence that Beijing is developing new cable-cutting technologies for potential wartime use.”
What happens if the cables are damaged?
Severing transcontinental data cables would have immense consequences, according to Kenny Huang, the head of the Asia Pacific Information Center (APIC), which serves as the Internet address registry for the Asia–Pacific region.
If the main cable is damaged, “you lose the entire Internet connectivity,” he told DW.
“If you lose the Internet connectivity, that means you lose everything,” he added.
An affected region would not even be able to use its own internal network, effectively transforming it into an information vacuum. In case of Taiwan, the island would be “blind,” with the fallout spanning far beyond communications and into sectors such as education, economy, agriculture and many others.
Other countries in the region are likely to face similar issues in case of an underwater attack. And even if the cables are not severed or damaged, they could be used to tap into transcontinental information networks.
“Rival states could exploit these weaknesses for intelligence gathering or to create strategic advantages in maritime security conflicts,” Global Defense Insight, an online magazine, warned in a report from February 2025.
Baltic Sea as a hybrid war proving ground
From a technical standpoint, destroying underwater cables is not overly difficult, said Johannes Peters from the Kiel University.
“It is enough to drag some sort of an anchor across the seabed, that will then pull on the cable and eventually snap it. You don’t need a particularly high-performance ship,” he told DW.
“China will be watching very carefully how the West responds to attacks on the undersea cables. It will try to identify the resulting problems of the Western nations — not only technical but also legal, stemming from international maritime law. In this respect, the Baltic Sea right now is a kind of a proving ground for maritime warfare, which is naturally being observed from other parts of the world.”
Can cables be protected?
This is one of the reasons that cables need more legal protection, including higher penalties for deliberate cutting of communication links, said Kenny Huang.
At the same time, there are technical steps that can be taken, according to the official, For example, once a cable has been damaged, the data traffic can be rerouted to a different cable or a different provider. A multi-level backup plan can make a difference.
At the same time, he warns that, in the event of a military attack on an undersea cable, “there’s no actor able to defend [against] that kind of attack.”
This is why countries in the region increasingly focus on prevention measures. Japan and its allies intend to eliminate Chinese companies from projects involving undersea cables if US investors and companies are already taking part, according to the CSIS report. Furthermore, Japan is now spacing out their cables across a larger area, so a single attack is not a threat to the whole system.
States can also limit naval traffic in certain areas and issue special permissions for vessels sailing near the cables, said Peters.
“Even the cables themselves can be partially protected by using appropriate sensors,” he added.
This article was originally published in German
