As the country has done before, Syria cut off the Internet for all its citizens yesterday. As in all Internet access has completely disappeared. Google's Transparency Report, which shows traffic to Google, reveals that Syria pretty much no longer exists on the Internet.
Back when the Syrian government blocked Internet access in November 2012, the outage lasted three days. There could be the slimmest of possibilities that an outsider was the culprit for the Internet outage, but that's extremely unlikely. Security experts say that in order for an outsider to pull this stunt, they would have to physically cut four cables (three under the sea, one on land) simultaneously. So yeah, this is the Syrian's government doing.
Security experts predict that the Syrian government has basically re-mapped where Internet addresses go in Syria (nowhere, since they don't know where to). CloudFare, an Internet security firm, described the situation to the NY Times:
“It’s akin to someone removing all the street signs into Syria”