Despite the common notion popularized by fiction, the majorities of communications do not pass through by satellites, but by cables placed on the seabed. About 250 cables connect continents and carry data, as well as telephone calls. The traffic is estimated at 99% in this way.
In case of problem on a submarine cable (cut or damaged), the Internet can slow down in concerned countries, as long as the operators reroute the connections. In March 2013 divers cut a cable causing an Internet slowdown in several countries, such as Pakistan.
Based on documents published by Edward Snowden, German newspapers have revealed that the British secret services are spying communications through the submarine cables which end up on their coasts. These cables link Europe to the United States, but also Russia.
To get this information, there are several ways. One of them is to read the optical network by causing a bend in the fiber to extract enough light to sniff data without interrupting the flow. This is difficult in an underwater environment, but quite possible on the cable ends.
In Great Britain, this method is not necessary because the secret services have the possibility to force the owners of cables (Vodafone Cable, British Telecommunications…) to participate in the surveillance in giving a direct access to the stations. Then, they just have to install monitoring equipment to record the data. By the cooperation agreement with Britain, the United States can also benefit from the information.
These cables are therefore very important strategic issues for the countries.