Underseas cables are vulnerable to attack and can take days to repair, potentially severing a country from the network

Tapping today’s fiber-optic cables is theoretically possible, but it is easier to cut or damage them and significantly impact the cables’ users. And while the exact location of cables is not publicly available, improvements to “bottom survey” equipment and unmanned undersea vehicles are making finding cables easier and faster. In time-sensitive military or diplomatic operations, the loss of communications for a few minutes or hours can be catastrophic. With financial transactions, the loss of even fractions of a second can cost millions of dollars as high-speed trades miss their targets and other transactions fail to go through or are lost entirely. The dozens of cable outages that occur each year do not cause a complete loss of service, but they do slow data-transfer speeds as information is re-routed through fewer intact cables. Most of these cable breaks happen in relatively shallow water, when rough weather moves cables around until they break or fishing trawlers catch a cable in a net. Some outages, however, have more nefarious origins. In 2013, three divers with hand tools cut the main cable connecting Egypt with Europe, reducing Egypt’s Internet bandwidth by 60%.

Repairing a submarine cable at sea is difficult and time consuming. First the break has to be located using built-in monitoring systems that can indicate the cable segment in which the break is likely to have occurred. Cable repair ships then must go to that location and pull up the cable until they get to the damaged spot. A new section of cable can then be spliced in, which can take several days to complete.