As the civil war rages on in Syria, Internet service was reportedly cut off nationwide on Thursday. Cellphone service has reportedly also been cut in "select areas," and landlines are said to be "working only sporadically."
The exclusive provider of Internet access in Syria is the state-run Syrian Telecommunications Establishment. Their network AS number is AS29386. The following network providers typically provide connectivity from Syria to the rest of the Internet: PCCW and Turk Telekom as the primary providers with Telecom Italia, TATA for additional capacity. When the outage happened, the BGP routes to Syrian IP space were all simultaneously withdrawn from all of Syria's upstream providers. The effect of this is that networks were unable to route traffic to Syrian IP space, effectively cutting the country off the Internet.
The Internet has been a strategic weapon for the uprising and the government alike, allowing activists to organize and communicate but also exposing them to surveillance. Fighters activists and ordinary citizens upload video of rebel exploits and government crackdowns but also exposing rebel atrocities -- making the Syrian conflict one of the most documented conflicts with the sheer amount of material available.