Thursday Internet traffic dropped off substantially to and from China. Paul Mozur of the Wall Street Journal's China Real Time blog tracked the outage as a data dropoff lasting from 11:00am to 1:00pm local time.
The interruption spawned a host of possible explanations. These included the powerful 8.6 magnitude earthquake the day before off the coast of Indonesia, a cinching down of the "Great Firewall of China" censorship system, a failure in the country's network backbone, and a software upgrade.
There is a bottleneck of undersea cables in the Malacca Straits which could have been affected by the quake. China is connected to the Internet from only three major points, as the Guardian notes in its coverage. This makes the country arguably more vulnerable than countries like the US.
However, Xu Chuanchao, an executive with Sohu, one of China's largest Web portals, posted to his microblog his opinion that "This malfunction is caused by the failure of China's backbone network and is under renovation."
The publication also pointed out that many "lesser known VPNs seemed to connect without any problems." and quoted David Wolf of Wolf Group Asia as saying, "It's possible they were short of capacity and that's why some people got through, but given that obscure VPNs were working I find that hard to believe."
According to Tech in Asia, (via China Digital Times), two of the largest Chinese ISPs, Telecom and Unicom, are denying knowledge of the source of the interruption but both insisted that a breakdown on their end was not to blame.
Mozur's reporting however, based on data from CloudFlare, indicated that the overwhelming majority of the dropoff was from Telecom and Unicom and it was almost exclusively HTTP traffic. This, according to CloudFlare CEO Matthew Prince indicates it was probably a result of filtering, "which suggests that someone made a mistake when filtering something—likely they filtered the entire internet.”
Tech in Asia's writer C. Custer theorized it was the test of a new government Internet "kill switch."