Countries such as China, India, Mexico, Israel and Vietnam, which have between 10 and 40 internationally connected service providers, are also at fairly low risk of total disconnection, Cowie said. The countries, about 72 in all, with fewer than 10 ISPs that are exposed to significant risk of total blackouts, he said. Among them are Oman, Uganda, Iran, Pakistan and Armenia. Though disconnection would not be especially easy, it could be achieved, he said. A total of 61 countries, including Syria, Tunisia, Libya and Ethiopia, have just one or two international ISPs and are st severe risk of disconnection.
For countries like the U.S., the bigger risk is Internet disruptions from attacks against the Internet's core Domain Name System (DNS) servers and other critical infrastructure, Morales from Arbor Networks said. Even here, it would be an enormous task to completely take down the Internet as was done in Syria, he said. "It would be very much harder to black out the Internet in the U.S. either willfully," or by attacking it, he said.
Jaikumar Vijayan covers data security and privacy issues, financial services security and e-voting for Computerworld. Follow Jaikumar on Twitter at @jaivijayan or subscribe to Jaikumar's RSS feed. His e-mail address is firstname.lastname@example.org.
Read more about networking in Computerworld's Networking Topic Center.