Why are subsea cables allegedly being tampered with, and what impact does it have on us all?

Every year, between 100 and 150 incidents involving subsea cables that carry internet connections from one country to another are recorded. In each of those cases, the cables incur so much damage that they’re severed or cut and have to be fixed in some way.

Many are accidents – but not all. This week, an incident occurred in the Baltic Sea, which politicians and experts are claiming was a deliberate attempt to tamper with the connection between Finland and Germany.

The C-Lion1 cable, which provides an internet link between the two countries, was damaged earlier this week. Who or what did it is still not certain, but Danish authorities have intercepted a Chinese vessel called the Yi Peng 3, which was travelling above the cable at the time it was damaged.

Politicians in Finland and Germany have said they believe the incident is evidence of “sabotage” by China or Russia – from where the Yi Peng 3 travelled before it damaged the subsea cable.

Why are cables being attacked?

The incident is one of many that has taken place around the world, with an increasing worry that attacking internet infrastructure is being used to try and harm the way of life of many people. In February 2023, China was alleged to have severed two cables bringing internet connections to an outlying island of Taiwan, disconnecting the island from the wider web. And other incidents occur with increasing regularity.

“There’s a concern that some of these things can look accidental but are actually on purpose,” says Doug Madory, head of internet analysis at Kentik.

One way of finding out who or what is responsible for the damage is to track the AIS, or Automatic Identification System, data that every ship should be transmitting while traversing the seas.

Some groups that are alleged to have sabotaged cables don’t bother to try and hide their crimes. Houthi rebels attacked and cut four major communication cables in the first few months of 2024 and had no reason to try and get plausible deniability for their actions.

Others, like Russia and China, have enough cover to claim that the incidents were accidents and not linked to their governments.

What impact do such attacks have?

The extent of a cable-cutting incident depends on where it happens. In the case of the 2023 attacks on the Taiwanese outlier island, the two cables cut were the only two bringing the internet to the island and its people. However, Madory says that the impact on the countries served by the C-Lion1 cable was minimal. The biggest impact, he said, was on latency, but that was minimal.

That’s in part because of the built-in redundancies around the world for more developed countries when it comes to internet cabling. More than 530 cables crisscross the planet, keeping countries connected. In more developed areas of the planet, spending on infrastructure is higher, meaning that backup cables could be used to reroute traffic in the event of a disaster.

However, in other parts of the world, where there are fewer backups, losing that connection can be a terminal issue for a country.

The Centre for Strategic and International Studies (CSIS), a non-profit think tank, has said that cables are the “soft underbelly of the global economy.” The world is building more and more cables to try and reduce the risk of something going catastrophically wrong if a single connection is cut, but it’s also incumbent on governments to do something.

One thing they could do is highlight how important it is that such sabotage is taken seriously and how severe the risk of penalties for meddling in other countries’ sovereign communications services is.