A vast behemoth that can route around outages and self-heal, the Internet has grown physically invulnerable to destruction by bombs, fires or natural disasters — within countries, at least. It’s “very richly interconnected,” said David Clark, a computer scientist at MIT who was a leader in the development of the Internet during the 1970s. “You would have to work real hard to find a small number of places where you could seriously disrupt connectivity.” On 9/11, for example, the destruction of the major switching center in south Manhattan disrupted service locally. But service was restored about 15 minutes later when the center “healed” as the built-in protocols routed users and information around the outage.

However, while it’s essentially impossible to cripple connectivity internally in a country, Clark said it is conceivable that one country could block another’s access to its share of the Internet cloud; this could be done by severing the actual cables that carry Internet data between the two countries. Thousands of miles of undersea fiber-optic cables that convey data from continent to continent rise out of the ocean in only a few dozen locations, branching out from those hubs to connect to millions of computers. But if someone were to blow up one of these hubs — the station in Miami, for example, which handles some 90 percent of the Internet traffic between North America and Latin America — the Internet connection between the two would be severely hampered until the infrastructure was repaired.