Submerged Vulnerabilities:

Although we rarely think about undersea cable networks, they are central to the modern world. Our very way of life depends on this hidden infrastructure of cables the diameter of a garden hose that crisscrosses the oceans. These cables form a global infrastructure that transmits almost all the data sent over the internet. With daily online financial transactions estimated at over $10 trillion, any disruption to this network would have an immediate effect on the global economy.

Today there are around 500 operational submarine cables worldwide, totaling well over a million kilometers of cable in a network that continues to grow. When someone reads an email, posts a video on social media, or consults a search engine, this information passes through an undersea fiber optic cable. Despite the centrality of submarine cables to the global economy and our daily lives, this network remains mostly unprotected. But should we worry?

Cables at Risk

The most recurrent threat to the cables—responsible for roughly 150 to 200 undersea cable faults every year—is accidental physical damage from commercial fishing and shipping as well as underwater earthquakes. In 2022, a volcanic eruption off Tonga snapped the only fiber cable connecting the island to the rest of the world.

Another potential hazard is that political adversaries could strategically disrupt international cable networks during times of conflict. Cutting cables is a highly disruptive tactic for military or government communications in the early stages of a conflict, since it could restrict or even fully eliminate internet access for the targeted population, in addition to causing economic difficulties for a rival power.

There are historical precedents for wartime cable cutting. In World Wars I and II, the first hostile acts by the British Royal Navy against Germany involved cutting telegraph cables between Germany and the Americas. In today’s world, NATO’s intelligence chief has recently warned that Russia is preparing to attack NATO members’ submarine cables if direct conflict erupts. In February of this year, Chinese vessels purposefully damaged two sea cables connected to the Taiwanese island of Matsu, which prevented the island’s 13,000 residents from accessing the internet.

Such attacks on submarine networks extend beyond physical cutting of cables. Malicious actors can also disrupt data flows by virtually hacking into the network management systems that private companies use to manage the data traffic that passes through these cables.

Challenges of Repair

In 2017, a single cable was accidentally cut by a ship’s anchor off the coast of Somalia. The resulting communications outage lasted three weeks and cost the country $10 million per day. There are other nations that rely on only one or two cables while others are connected to multiple cables. The speed of repair and recovery is even more critical in the former case.

It takes some 20 hours to drop a grapnel to a depth of 6,000 meters—the maximum feasible depth for cable repair operations. Cables in deeper trenches are not repaired directly but rather are spliced at either side of the trench.

The ability to repair the network if multiple cables are damaged—whether by natural hazards or malicious actors—is seriously hampered by the lack of cable repair ships. There are only 60 such ships operating worldwide. Many of these vessels were commissioned during the internet boom in the 1990s and are rapidly aging. The insufficient number of repair ships is as dire for cable infrastructure today as a lack of emergency vehicles would be for fire-fighting operations.

Building Resilience

Protecting cables that stretch for thousands of miles across the deep ocean floor is extremely challenging and expensive. Large-scale undersea cables cost several hundreds of millions of dollars. They are usually paid for by a consortium of technology or telecom companies that can share costs and risks. This lack of formal state ownership of cables means that they do not have strong protections under international law. Nevertheless, governments could do more to support this infrastructure, including by expanding the overstretched global fleet of cable repair vessels. National governments could also ensure that operating companies adhere to the highest standards.

Best practices for protecting cables include building network resiliency and redundancy and improving monitoring. Ensuring the resiliency of these cable networks should be a collective global priority. This should include preparing contingency plans in close coordination with the private sector in order to mitigate the consequences of intended or unintended cable cuts.

As for redundancy, key data traffic routes could be backed up with extra "dark" cables, which would ideally not be marked on charts and would be buried as deeply as possible. For better detection of threats, cables could be fitted with sensors to identify the sonar frequencies used by submersibles attempting interference. As a result of new developments in the field, deploying a fleet of unmanned underwater vehicles (UUVs) to patrol sections of cable networks is also now more practical and affordable.