A number of Chinese netizens report that since May 6 2011 visiting overseas website via China Telecom and China Unicom has become highly unstable. This time the disruption mainly affected corporate connections, including university, while ADSL connection at home performs normally.
Some technology bloggers point out that the Great Fire Wall is now able to monitor data flow of local IP and impose restriction when it detect large amount of access to certain overseas IP addresses. Some are worried that the mechanism may result in a de facto white listing of overseas websites.
Corporate and university connection affected
Prominent Technology blogger William Long points out that the blocking this time is targeted at corporate user in order to stop people from visiting overseas website via corporate network and connection.
He runs a test in his office at Shenzhen and found out that he cannot connect to certain overseas IP addresses (126.96.36.199). Below shows the detail of the test results:
The Southern Medical University also has suffered from the disruption and explained the situation that China Telecom has restricted the IP access of the university to overseas websites. Zhejiang University also has similar problem [zh], the school VPN's overseas connection has been disrupted. (via William Long)
Data flow monitored
In Sina Microblog, many re-post the following information:
VPN and circumvention tools forbiddened
In order to tackle with the problem, the IT department of certain corporate has issued the following notices: (via Twitter user @yegle)
原文转载：各位同学， 请大家在使用公司内部网络时，不要使用翻墙工具和VPN等方式访问境外网络信息。 此行为可能导致公司网络出口被封（如：google，msn等正常境外网络访问不稳定），并会为公司和个人带来不必要的麻烦。 请大家在日常工作中一定注意避免。
A notice from the Chinese Academy of Sciences has confirmed netizens’ speculation: