Submarine cable security is all at sea
• The Register Mon 29 Sep 2025 // 08:01 UTC by Danny Bradbury Feature: Guess how much of our direct transatlantic data capacity runs through two cables in Bude? The first transatlantic cable, laid in 1858, delivered a little over 700 messages before promptly dying a few weeks later. 167 years on, the undersea cables connecting the UK to the outside world process £220 billion in daily financial transactions. Now, the UK Parliament's Joint Committee on National Security Strategy (JCNSS) has told the government that it has to do a better job of protecting them. The Committee's report, released on September 19, calls the government "too timid" in its approach to protecting the cables that snake from the UK to various destinations around the world. It warns that "security vulnerabilities abound" in the UK's undersea cable infrastructure, when even a simple anchor-drag can cause major damage. There are 64 cables connecting the UK to the outside world, according to the report, carrying most of the country's internet traffic. Satellites can't shoulder the data volumes involved, are too expensive, and only account for around 5 percent of traffic globally. These cables are invaluable to the UK economy, but they're also difficult to protect. They are heavily shielded in the shallow sea close to those points. That's because accidental damage from fishing operations and other vessels is common. On average, around 200 cables suffer faults each year. But as they get further out, the shielding is less robust. Instead, the companies that lay the cables rely on the depth of the sea to do its job (you'll be pleased to hear that sharks don't generally munch on them). The report praises a strong cable infrastructure, and admits that in some areas at least we have the redundancy in the cable infrastructure to handle disruptions. For example, it notes that 75 percent of UK transatlantic traffic routes through two cables that come ashore in Bude, Cornwall. That seems like quite the vulnerability, but it acknowledges that we have plenty of infrastructure to route around if anything happened to them. There is "no imminent threat to the UK's national connectivity," it soothes. But it simultaneously cautions against adopting what it describes as "business-as-usual" views in the industry. The government "focuses too much on having 'lots of cables' and pays insufficient attention to the system's actual ability to absorb unexpected shocks," it frets. It warns that "the impacts on connectivity would be much more serious," if onward connections to Europe suffered as part of a coordinated attack. "While our national connectivity does not face immediate danger, we must prepare for the possibility that our cables can be threatened in the event of a security crisis," it says. Reds on the sea bed Who is the most likely to mount such an attack, if anyone? Russia seems front and center, according to experts. It has reportedly been studying the topic for years. Keir Giles, director at The Centre for International Cyber Conflict and senior consulting fellow of the Russia and Eurasia Programme at Chatham House, argues that Russia has a long history of information warfare that stepped up after it annexed Crimea in 2014. "The thinking part of the Russian military suddenly decided 'actually, this information isolation is the way to go, because it appears to win wars for us without having to fight them'," Giles says, adding that this approach is often combined with choke holds on land-based information sources. Cutting off the population in the target area from any source of information other than what the Russian troops feed them achieves results at low cost. In a 2021 paper he co-wrote for the NATO Cooperative Cyber Defence Centre of Excellence, he pointed to the Glavnoye upravleniye glubokovodnykh issledovaniy (Main Directorate for Deep-Water Research, or GUGI), a secretive Russian agency responsible for analyzing undersea cables for intelligence or disruption. According to the JCNSS report, this organization operates the Losharik, a titanium-hulled submarine capable of targeting cables at extreme depth. Shenanigans under the sea You don't need a fancy submarine to snag a cable, as long as you're prepared to do it in plain sight closer to the coast. The JNCSS report points to several incidents around the UK and the Baltics. November last year saw two incidents. In the first, Chinese-flagged cargo vessel Yi Peng 3 dragged its anchor for 300km and cut two cables between Sweden and Lithuania. That same month, the UK and Irish navies shadowed Yantar, a Russian research ship loitering around UK cable infrastructure in the Irish sea. The following month saw Cook Islands-flagged ship Eagle S damage one power cable and three data cables linking Finland and Estonia. This May, unaffiliated vessel Jaguar approached an underseas cable off Estonia and was escorted out of the country's waters. The real problem with brute-force physical damage from vessels is that it's difficult to prove that it's intentional. On one hand, it's perfect for an aggressor's plausible deniability, and could also be a way to test the boundaries of what NATO is willing to tolerate. On the other, it could really be nothing. "Attribution of sabotage to critical undersea infrastructure is difficult to prove, a situation significantly complicated by the prevalence of under-regulated and illegal shipping activities, sometimes referred to as the shadow fleet," a spokesperson for NATO told us. "I'd push back on an assertion of a coordinated campaign," says Alan Mauldin, research director at analyst company TeleGeography, which examines undersea cable infrastructure warns. He questions assumptions that the Baltic cable damage was anything other than a SNAFU. The Washington Post also reported comment from officials on both sides of the Atlantic that the Baltic anchor-dragging was probably accidental. Giles scoffs at that. "Somebody had been working very hard to persuade countries across Europe that this sudden spate of cables being broken in the Baltic Sea, one after another, was all an accident, and they were trying to say that it's possible for ships to drag their anchors without noticing," he says. One would hope that international governance frameworks could help. The UN Convention on the Law of the Sea [PDF] has a provision against messing with undersea cables, but many states haven't enacted the agreement. In any case, plausible deniability makes things more difficult. "The main challenge in making meaningful governance reforms to secure submarine cables is figuring out what these could be. Making fishing or anchoring accidents illegal would be disproportionate," says Anniki Mikelsaar, doctoral researcher at Oxford University's Oxford Internet Institute. "As there might be some regulatory friction, regional frameworks could be a meaningful avenue to increase submarine cable security." The difficulty in pinning down intent hasn't stopped NATO from stepping in. In January it launched Baltic Sentry, an initiative to protect undersea infrastructure in the region. That effort includes frigates, patrol aircraft, and naval drones to keep an eye on what happens both above and below the waves. Preparing for the worst Regardless of whether vessels are doing this deliberately or by accident, we have to be prepared for it, especially as cable installation shows no sign of slowing. Increasing bandwidth needs will boost global cable kilometers by 48 percent between now and 2040, says TeleGeography, adding that annual repairs will increase 36 percent between now and 2040. "Many cable maintenance ships are reaching the end of their design life cycle, so more investment into upgrading the fleets is needed. This is important to make repairs faster," says Mikelsaar. There are 62 vessels capable of cable maintenance today, and TeleGeography predicts that'll be enough for the next 15 years. However, it takes time to build these vessels and train the operators, meaning that we'll need to start delivering new vessels soon. The problem for the UK is that it doesn't own any of that repair capacity, says the JNSS. It can take a long time to travel to a cable and repair it, and ships can only work on one at a time. The Committee reported that the UK doesn't own any sovereign repair capacity, and advises that it gets some, prescribing a repair ship by 2030. "This could be leased to industry on favorable terms during peacetime and made available for Government use in a crisis," it says, adding that the Navy should establish a set of reservists that will be trained and ready to operate the vessel. Sir Chris Bryant MP, the Minister for Data Protection and Telecoms, told the Committee it that it was being apocalyptic and "over-egging the pudding" by examining the possibility of a co-ordinated attack. "We disagree," the Committee said in the report, arguing that the security situation in the next decade is uncertain. "Focusing on fishing accidents and low-level sabotage is no longer good enough," the report adds. "The UK faces a strategic vulnerability in the event of hostilities. Publicly signaling tougher defensive preparations is vital, and may reduce the likelihood of adversaries mounting a sabotage effort in the first place." To that end, it has made a battery of recommendations. These include building the risk of a coordinated campaign against undersea infrastructure into its risk scenarios, and protecting the stations - often in remote coastal locations - where the cables come onto land. The report also recommends that the Department for Science, Innovation and Technology (DSIT) ensures all lead departments have detailed sector-by-sector technical impact studies addressing widespread cable outages. "Government works around the clock to ensure our subsea cable infrastructure is resilient and can withstand hostile and non-hostile threats," DSIT told El Reg, adding that when breaks happen, the UK has some of the faste...
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