Companies that track Internet traffic saw a precipitous drop in Syria Tuesday. Requests for everything from YouTube, news sites and yes, even porn outside the country came to a screeching halt at 2:48 p.m. EST. 

“All of those connections were  turned off with literally the stroke of a command on a computer,” said Matthew Prince, CEO of website security firm CloudFlare.

Syria came back online this morning at 10:12 a.m. EST and state news services are reporting a physical failure was to blame.

How true is that? Somewhat. The physical structure of the Internet in Syria did play a key role.

“Certain countries have limited access to the internet. In the case of Syria, there are only four connection points, and they’re all run by the national Syrian telecommunications company,” Prince said.

The motivation? Likely political.

Prince and his colleagues rewound and watched the routers that link Syria to the broader internet turn out like little lights, one by one, which they captured in this video:

Syria from CloudFlare on Vimeo.

Internet security analyst James Cowie at Renesys says other countries with structures similar to Syria’s are at risk. Among them: Cuba, North Korea, Libya and Tunisia.

But it’s not all countries with tense U.S. relationships, or recent revolutions. Even Greenland is at risk.

What about the U.S.? Prince says the big roadblock is there’s not one company or central agency controlling every cable. That and the number of physical connections from the U.S. (and other larger countries) to the outside world make it unlikely.