Over 99% of the transcontinental internet traffic goes through a network of 280 sets of undersea cables.

How vulnerable are these to deliberate sabotage by the major powers?

I'd rather not focus much on why any nation would want to attempt such a thing or to what degree principles of MAD will apply, I'm just assuming that it's a war scenario and such intentional sabotage is desirable.

Such sabotage won't actually shut down the internet rather it would only slow it down. If the slow down is significant enough it could have serious impact on productivity, and it would cost more to send the same amount of data. Or certain kinds of internet traffic might get banned altogether by the governments in favour of maintaining higher bandwidth for more important traffic. Again this is another discussion that's out of the scope of this question, also it's not something that's easy to predict and will depend on the nature of the war/emergency.

I'm just asking how much would it cost to do it (sever say, 50% of the cables)? Is it possible at all? What technology would work best (I'm assuming some sort of robots but not 100% sure)?

Also take into account the fact that the sabotage operations will probably have to be geographically distributed and/or fast and/or discreet enough (with options for plausible deniability and blaming others nations for the sabotage) ... If you set up an entire city just to create the infrastructure required for the operation there's a good chance you could get bombed or nuked before the operation succeeds.

  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$
    – L.Dutch
    Commented Feb 13, 2019 at 19:37
  • $\begingroup$ This is how you get an undersea cable out of the sea: youtube.com/watch?v=MDSgYGL7gHc $\endgroup$
    – patstew
    Commented Feb 13, 2019 at 21:23
  • $\begingroup$ @L.Dutch Can someone explain why this is off-topic? Real world topics are allowed, right? worldbuilding.meta.stackexchange.com/q/6161/5147 $\endgroup$ Commented Feb 14, 2019 at 6:45
  • $\begingroup$ @ghosts_in_the_code, I am not one of those who VTC. So I cannot explain their reasons. $\endgroup$
    – L.Dutch
    Commented Feb 14, 2019 at 6:54

5 Answers 5


The power who wants to cut the cables is China. The U.S.A. has no reason whatsoever to cut the cables, because they control the core internet routing tables and they can obtain the same effect by tapping a few keys; Russia doesn't have enough naval vessels; India will never want to cut the cables because a lot of their income depends on providing high-quality low-price services over the Internet; Pakistan / Iran / other wannabes don't even begin to have the resources to do it.

  • "I'm just asking how much would it cost to do it (sever say, 50% of the cables)?"

    1. There is no point in cutting 50% of the cables. Either you cut all (or at leat almost all) the cables reaching the enemy or adversary, or the entire exercise is pointless. There is a lot of overcapacity, cutting half the cables will cause only very minor inconvenience.

    2. As an opening just before the shooting starts, it's not that hard for China to do. The cables themselves are not armored or guarded in any way, so all they have to do is send out a few hundred destroyers armed with long steel cables with hooks attached and drag them crosswise over the cable.

    3. After the shooting starts, it's almost impossible to do. Any Chinese vessel trying to leave the protective arms of the mother country and reach open ocean will meet with a watery grave. The U.S.A. has satellites, and sonar networks, and submarines, and more naval vessels than everybody else combined.

      (Of course the war is China against the U.S.A. In a war with Russia there is no point the cut the cables -- the Russian Supreme Internet Censorship Authority (Roskomnadzor would actually thank you for such a service); the only other possible enemy of China is India, and the benevolent Chinese Communist Party knows very well that a war with India would be unprofitable.)

  • "Is it possible at all? What technology would work best (I'm assuming some sort of robots but not 100% sure)?"

    Surprinsingly primitive technology. Get a small-ish naval ship with a few thousand meters of steel cable aboard. Affix a bunch of hooks at the end of the cable. Throw the end of the cable with the hooks overboard. Drag the hooks across the cable. Bam, done.

    Don't try to be smart. Submarines don't work -- nobody has enough submarines to do this, not even the U.S.A. Robots are useless -- there is no point in using a very expensive robot when a hook at the end of a dumb cable will do the job.

  • "Also take into account the fact that the sabotage operations will probably have to be geographically distributed and/or fast and/or discreet enough (with options for plausible deniability and blaming others nations for the sabotage)"

    Well, duh. As soon as the Americans notice that somebody is cutting Internet cables wholesale the mighty U. S. Navy will become very very interested in finding out who exactly is playing with the livelihood of Amazon, Google, AT&T, etc. etc. The entire exercise is worthwhile only if all the cables can be cut more or less at the same time, and then only as a first act before an actually shooting war. As for plausible deniability, forget it. Ships are big are hard to hide.

    (P.S. That's why you need naval ships. The actions must be co-ordinated, and you really really don't want to tell civilians what you are up to.)

  • $\begingroup$ From the assertions you make in the answer, even doing this just before shooting starts would be a suicide mission for the Chinese fleet involved in the exercise. They couldn't return to base before being intercepted. $\endgroup$
    – alephzero
    Commented Feb 13, 2019 at 18:23
  • 2
    $\begingroup$ Cutting the cables is trivial: just send a cargo ship or a fishing trawler out to drag its anchor on an appropriate section of seabed. $\endgroup$
    – Mark
    Commented Feb 13, 2019 at 21:14
  • 2
    $\begingroup$ @Mark: Yes, but the problem is how to co-ordinate the cutting activities. Involving civilian vessels greatly increases risk that someone will tell the Americans about the plan. There are very many cables to cut. $\endgroup$
    – AlexP
    Commented Feb 13, 2019 at 21:26
  • $\begingroup$ You say the US government can practically shut down the entire internet (or at least domestically) if they wanted to. Out of curiosity, do you have some source for that, since that's a major vulnerability in its own right. I thought the routing was done majorly by ISPs who, though are legally subject to the state, have the potential to refuse or delay. $\endgroup$ Commented Feb 14, 2019 at 4:05
  • 1
    $\begingroup$ @ghosts_in_the_code: Of course the core data carriers can refuse. The military are also known for their shyness, infinite patience and understanding. $\endgroup$
    – AlexP
    Commented Feb 14, 2019 at 6:27

Less vulnerable than they were 10 years ago and it's getting better.

In 2008 I lost my phone. You wouldn't think anything of it, but it just happened that the same day someone dropped anchor on an undersea cable near Egypt. That anchor cut off the connection from the UK to the Indian call centre my mobile operator used so I couldn't contact them about it.

The powers that be are very aware of the vulnerability of the undersea cables. They used to primarily only guard them at the landing points, but they're also building up redundancy in the system as the connections become ever more critical to day to day life.

Some countries or regions will be easier to cut off from the rest than others. The islands (UK, NZ, Aus), isolated continents (Americas), those behind closed firewalls necessitating limited external connections (many Arab countries, China, soon Russia).

As mentioned in the comments, satellite connections do exist but they're far harder to access. Also weapons to solve that do exist, though only available to certain states.

In terms of the easiest way to do it, underwater ROV is effective but expensive. Dragging a large ship anchor through where the cable lies is also effective, but probably surprisingly expensive, large ships cost a lot to run.

  • 1
    $\begingroup$ Yes we're aware that they're aware (obviously right?). I'm asking is it still possible. You also mentioned it's expensive. But how expensive? Government spending on militaries runs into billions of dollars so it might still be cheaper than alternative forms of warfare. $\endgroup$ Commented Feb 13, 2019 at 15:26
  • $\begingroup$ @ghosts_in_the_code, it's a military act, but it's not warfare in its own right, perhaps it's better to tap the connection rather than cut it? Would they cut the connection themselves to stop the effect of you doing it? To stop you listening to it? $\endgroup$
    – Separatrix
    Commented Feb 13, 2019 at 15:30
  • 4
    $\begingroup$ 1. Encryption? Tapping can't bypass that, right? They can only look for poorly encrypted and unencrypted data (which will be even harder to find if it is well known that tapping happens). 2. The amount of data being conveyed so vast it would be expensive to perform computation on it or hunt for relevant records. 3. Blowing it up is definitely easier than tapping into it. $\endgroup$ Commented Feb 13, 2019 at 15:35
  • $\begingroup$ @ghosts_in_the_code. yes tapping it is hard, that's why everyone puts so much time, effort, and money into it, because it's worth it. $\endgroup$
    – Separatrix
    Commented Feb 13, 2019 at 15:44
  • 1
    $\begingroup$ I don't think you're appreciating @ghosts_in_the_code 's second point. Even if you could store and search that information, 99.99...% of it is worthless... this is orders of magnitude harder than finding a needle in a haystack. $\endgroup$
    – spinodal
    Commented Feb 13, 2019 at 18:48

Could a great power sabotage these cables? The answer is definitely yes. To do that, they would need submarines and/or ships that could drag a big anchor someplace on the ocean floor to cut the cable.

How hard would that be in a war scenario depends on the capabilities of who is going to war. If it is known that the cables are desirable to tap or cut, warships will be tasked with defending them. Then the effort required to cut them increases, because the force who wants to cut the cable will need to commit more resources to fight off the defenders and then cut the cables.

This is a problem that has been studied; the SOSUS warning system in the North Atlantic is essentially a series of cables with microphones attached to them, that were draped in several places in order to detect Soviet submarines. They would likely be targets for the Soviet Navy in the event of World War III. I do not know offhand how difficult it would be to cut those cables but I’m certain the Soviet Navy had a plan to do so and that the US Navy anticipated it. It might be a good case to research.

  • 1
    $\begingroup$ Cutting cables is old hat. At the beginning of WWI, the British cut German cables to the US so Germany would have to route communications through some place the British could monitor. $\endgroup$ Commented Feb 13, 2019 at 18:57

Search for phrases like "maritime cable cut" and top of the list just now was a BBC article from 2017 discussing just such a scenario. Sites like The Register regularly carry stories of accidental cable cuts - there are maintenance ships located around the world built specifically to locate and repair cables. I'm sure I've read other articles on The Register about how the cables are laid, repaired as well as how they have in the past been tapped.

In regards to cutting, as has been proven several times a ship dropping anchor or even trawling in the wrong place can do it easily. This shouldn't happen as the cable locations are known and charted. It doesn't take a lot to imagine somebody could send a fleet of "fishing boats" out to launch a coordinated cable cutting attack.


No great power or anything needed. Some storm, anchors and weights for nets of small fishing boats also do the trick, that even quite frequently as well as even thieves. One only careful can guess, but 30% are almost always more or less damaged. This does not mean, there is no internet ... it just gonna be slower, especially during peak hours on international basis. Internet uses some quite sophisticated protocols for it's traffic, 'scanning' and adjusting itself, similar to electricity or road traffic - following the ways of least resistance, managed by routers - 'Hey, have a long time not heard back, try another one'. So in worse cases it even can be routed via power cables or electric fence, satellites and other media. Until routers have picked up new routes, delays/low speeds might happen, same as traffic jams occur and finally via side roads dissolve. Can one really take a country take a country offline - ot really, as today's cables are just another medium for communication - today no bus, ok, take a car or even walk

  • $\begingroup$ Welcome to Worldbuilding, Olaf! If you have a moment, please take the tour and visit the help center to learn more about the site. You may also find Worldbuilding Meta and The Sandbox useful. Here is a meta post on the culture and style of Worldbuilding.SE, just to help you understand our scope and methods, and how we do things here. Have fun! $\endgroup$
    – Gryphon
    Commented Feb 13, 2019 at 19:47
  • $\begingroup$ Hello, Olaf. Could you take a moment to clarify your post? It's a bit difficult to read. I'm not convinced a small fishing boat with an anchor could cut the cables. Can you cite proof that 30% of the cables are always more-or-less damaged? Are you sure communication can occur in ways other than these cables and satellites? I think I need proof that com can be routed through power cables and "electric fence" (whatever that means in an ocean). Thanks! $\endgroup$
    – JBH
    Commented Feb 13, 2019 at 20:07
  • $\begingroup$ Not sure, what is there difficult.., it's actually low technical explained. I still try again: those cables, a lot, roughly 30% are almost always more or less damaged. As internet is a medium, like a means of transport, humans will find other ways, a side road in a traffic jam. Same, one use different means of transportation, same can be applied to the internet. There even was a time, where people had a subscription, which was limited by minutes and dialing up to the internet and finally, they could maybe connect to ....Yes, internet is more. It's something like human greed - can you stop it? $\endgroup$
    – Olaf
    Commented Feb 13, 2019 at 20:26

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