Key Undersea Cables Break (Again) in the Mediterranean

For the second time this year, multiple undersea cables that handle a large amount of transcontinental network traffic have failed somewhere under the Mediterranean Sea. Two fiber optic cable breaks in January 2008 near the coast of Egypt limited the Internet connectivity of millions of people in the Middle East and Asia for several days. In this current incident, three such cables have reportedly stopped functioning with similar impact expected.

The specific cables involved in this incident are so integral to the routing of Internet traffic that each has a name: SEA-ME-WE 3 (a.k.a. SMW-3), SEA-ME-WE 4 (SMW-4) and FLAG. Undersea network cables like these typically sit on the sea floor or are buried to fairly shallow depths under sediment. Possible causes of this incident include damage from a ship's underwater anchor (cause of the January failure), an earthquake, or an act of terrorism. While it's also conceivable that the cables suffered an internal technical malfunction, it's extremely unlikely that all three of them would each fail this way within one hour of each other.

Edit: A look at undersea cable repairs underway in the Mediterranean (22-Dec-08)