Undersea cables carry most international internet traffic, and they are now treated as security targets. A new book, Undersea War, argues that the threats to them are growing faster than the means to protect them.
Key takeaways
- Undersea fibre-optic cables carry most of the data that moves between continents, so damage to them can disrupt communications, finance and government services.
- Ars Technica reports on Elisabeth Braw’s book Undersea War, which examines the rising risks to infrastructure on the seabed.
- Most undersea cables are privately owned and lie in international waters, which leaves no single state clearly responsible for protecting them.
- When a cable is damaged, it is often hard to tell whether an accident or deliberate interference caused it, and that makes any response more difficult.
- Better repair capacity, monitoring and international cooperation are widely discussed as the main ways to reduce the risk.
What is happening to the internet’s undersea infrastructure?
Under the world’s oceans lies a network of fibre-optic cables that carries most of the internet traffic between countries and continents. Pipelines carrying gas and oil, and power cables linking national grids and offshore wind farms, share the same seabed. This infrastructure was built mainly for commercial reasons. For most of its history, the people running it worried mostly about accidents, such as fishing trawlers and ship anchors dragging across the seabed, or about natural events like underwater landslides and earthquakes.
That picture is changing. Governments, security analysts and the companies that run these systems increasingly see undersea infrastructure as a possible target in disputes between states. A cable could be cut, tampered with or watched in ways that fall short of open conflict but still cause real damage. The concern is that the backbone of the global economy is exposed and only lightly defended, and that someone could exploit this deliberately.
Why is this in the news now?
The immediate reason is the publication of Undersea War, a book by Elisabeth Braw that looks at the growing risks to seabed infrastructure. Ars Technica reports on the book and its argument that undersea links are moving into a more dangerous period. This summary does not cover the detailed findings, case studies or recommendations in the book, and readers who want the author’s full argument should go to the book itself.
The book appears at a time of wider public attention to the subject. In recent years, damage to cables and pipelines in waters such as the Baltic Sea has prompted investigations into whether ships had damaged them on purpose. Several of those cases have not produced public conclusions. That uncertainty has kept the issue on the agenda of governments and defence alliances.
How do undersea cables work, and why are they so exposed?
An undersea communications cable is a bundle of optical fibres inside protective layers. Near the shore, where fishing and shipping are heaviest, cables are usually armoured and often buried in the seabed. In deep water they tend to be thinner and simply rest on the ocean floor. Along the route, powered repeaters boost the light signals so that data can cross thousands of kilometres.
Several features make the system vulnerable. Cable routes are not secret, because they are often marked on nautical charts so that ships know to avoid them. Cables come ashore at a fairly small number of landing stations, and these can become points of concentration. Fixing a cable needs specialised repair ships, and these are in limited supply worldwide, so a break can take a long time to repair. The network has a lot of redundancy: when one cable fails, traffic usually shifts to others. That redundancy is uneven, though. Some islands and smaller countries depend on only one or two links.
Ownership and law add to the difficulty. Most cables belong to private consortia of telecommunications operators and, more and more, large technology companies. In international waters, the legal powers of any single state are limited. As a result, protecting the cables does not sit neatly with any one government, navy or company.
Who is affected, and in what ways?
In everyday life, almost everyone who uses the internet is affected, even though few people ever think about the cables. Messages, video calls, cloud services and online payments that cross borders mostly travel through undersea links. Satellites handle only a small share of this traffic.
Some groups are more exposed than others. Countries and territories with few cable connections can lose much of their connectivity when a single cable is damaged. Banks and payment systems rely on fast, dependable links between financial centres. Militaries and governments use commercial cables for some communications. Energy systems are increasingly at risk too, as more countries link their power grids under the sea and rely on offshore generation.
Cable owners and insurers carry the costs of repairs and outages. Coastal states face the problem of watching vast areas of sea with limited ships and sensors.
Where do informed observers disagree?
One debate is about how much of the damage is deliberate. Accidents caused by anchors and fishing gear have long been the most common cause of cable faults. Some analysts warn against assuming sabotage every time a cable breaks. Others argue that this very ambiguity is what makes seabed infrastructure attractive to a hostile actor, because it is hard to tell sabotage from an accident, and that deniability makes a response harder.
A second disagreement concerns responsibility. Some argue that navies and governments should take a much larger role in patrolling and protecting undersea assets. Others point out that the infrastructure is privately owned and spread across oceans, and that resilience is cheaper and more realistic than defence: more cables, more varied routes and faster repairs.
A third question is legal. The international rules governing cables were written mainly with accidental damage in mind. Experts differ on whether those rules are adequate for deliberate interference, and on how states can lawfully act against vessels in international waters.
What are the practical implications?
For governments, the issue is about building resilience. Measures commonly discussed include mapping which cables are critical, investing in repair ships, encouraging new routes that avoid chokepoints, and sharing information between countries and with operators. Some states have started treating undersea infrastructure explicitly as part of national security planning.
For companies that depend on international connectivity, the lesson is a familiar one from cybersecurity: assume that any single link can fail. Organisations can ask their network and cloud providers how traffic is routed, and whether services can continue if a particular route is cut.
For individuals, the practical effect is usually invisible, because traffic is rerouted automatically. When an outage does occur, it tends to show up as slower connections or as services in some regions becoming unavailable for a time.
What should readers watch next?
Several developments are worth following. Public findings from investigations into past incidents could clarify how often cable damage is deliberate. Defence alliances and coastal states may expand seabed monitoring, including the use of sensors and uncrewed vessels. Decisions about where new cables are laid, and who builds and owns them, will also shape the network’s security. Debate over updating international law for deliberate interference on the seabed is likely to continue. How much of the analysis in Undersea War feeds into policy discussions is not yet known.
Frequently asked questions
How much internet traffic goes through undersea cables?
Most international internet traffic travels through undersea fibre-optic cables rather than satellites. Cables offer much greater capacity and lower delay, so they carry the bulk of data between continents, including web traffic, cloud services, video calls and financial transactions. Satellites play a supporting role, mainly for remote areas, ships and aircraft. Exact shares vary by source and change over time, so any precise figure should be checked against current industry data.
What usually causes undersea cable damage?
Most cable faults have historically come from accidents, especially fishing gear and ship anchors dragging along the seabed in shallow coastal waters. Natural events such as underwater landslides and earthquakes also cause breaks. Deliberate damage is the newer concern. It is difficult to prove because a ship dragging its anchor may look the same whether the act was intentional or careless. This ambiguity is central to current security debates about seabed infrastructure.
Can one cut cable take a country offline?
For most large, well-connected countries, a single cable cut causes little visible disruption, because traffic is automatically rerouted through other cables. Smaller countries and islands that rely on only one or two connections are far more exposed. For them, a single break can severely reduce internet access until repairs are completed. Repairs depend on specialised ships, so restoring service can take a long time.
Who owns and protects undersea cables?
Most undersea communications cables belong to private companies or consortia, including telecommunications operators and large technology firms. Their routes often pass through international waters, where no single government has full authority. Protection is therefore shared between operators, coastal states, navies and international bodies, without one clearly responsible party. Many analysts see this fragmented responsibility as a main reason the infrastructure is considered vulnerable to deliberate interference.
What is the book Undersea War about?
Undersea War is a book by Elisabeth Braw that examines the rising risks to infrastructure on the seabed, including the cables that carry internet traffic. Ars Technica reports on the book and its argument that this infrastructure is becoming more exposed to danger. This article does not reproduce the book’s specific findings, examples or recommendations. Readers wanting the full analysis should consult the book directly.
How can undersea cables be made more secure?
Commonly discussed measures include laying more cables along varied routes so that traffic has alternatives, increasing the number of repair ships, monitoring the seabed with sensors and patrols, and improving information sharing between governments and operators. Legal reform for deliberate interference in international waters is also debated. Most experts treat resilience, meaning fast recovery and redundancy, as just as important as attempts to physically guard such long and remote infrastructure.
Sources and further reading
- Ars Technica: technology publication reporting on the book Undersea War and its argument about rising risks to seabed infrastructure.
- Undersea War: book by Elisabeth Braw on the security of undersea infrastructure, the primary work discussed.
- International Cable Protection Committee: industry body publishing general material on cable faults, protection and repair.
- United Nations Convention on the Law of the Sea: the international legal framework covering submarine cables and pipelines.
Surfaced from the rss:arstechnica signal “undersea infrastructure security book”. AI-assisted draft, editorially reviewed.
