This piece from the website International Business Times discusses how Libya recently shut off the internet in the country again (they did it once briefly in February), but they discuss how it’s different than what happened in Egypt. Here’s their explanation:
In Egypt, the government simply told the Internet service providers to shut the servers down. Technically, it was not very sophisticated. If a computer from another country tried to “ping” a server in Egypt, there was simply no answer.
This time, the servers in Libya are answering, in the sense that the route is clear and open. But there is no traffic. If one were to try and send a data packet from Libya to the U.S., for example, the server in Libya would send it to a “black hole route,” Cowie said. That means it would be held in place. The sender might never know what happened.
The rest of the article can be found here: http://www.ibtimes.com/articles/118969/20110304/libya-cuts-off-internet-engages-kill-switch.htm