"Physically breaking the links is complicated," Joffe said. "There are thousands of such links. So the easiest way is to configure the routers to withdraw the BGP announcements. All it takes is just one entry in the router's configuration file."

Unlike DNS entries, which are cached and so take hours, sometimes days to propagate throughout the world's DNS servers, by discontinuing BGP routing announcements, Egyptian ISPs were able to quickly disconnect from the Internet.

"As soon as that happens, seconds in some cases, minutes usually, the whole Internet knows that there are no pathways to those ISPs," Toonk said.

"One or two minutes, and it's done," Joffe echoed.

Egypt's digital blockade, called an by other network experts today, is the equivalent of isolating a castle under siege, Joffe added.