According to Renesys, all of Syria's 84 IP address blocks are unreachable. The company's traceroutes identified five networks that use Syrian-registered IP space and host Syrian content, but these traces lead Tata Communications and offshore destinations. "[These networks] perhaps [are] not subject to whatever killswitch was thrown today within Syria," Renesys wrote in a blog post.
Akamai confirmed the Renesys report and published a traffic chart that visualizes the sudden traffic drop at 10:26 UTC/GMT.
Arbor networks also documented the shutdown of Syria's Internet with a similar characteristic as the shutdown of the Internet in Egypt in January 2011. Egypt was offline nearly seven days back then.