无界网络 (Ultrasurf / Wujie wangluo) is a free Internet censorship circumvention tool. Ultrasurf was originally designed to enable internet users in China to safely bypass China’s Golden shield, but now has as many as eleven million users worldwide.
Why it is blocked: Besides the fact that the software punches a hole through China’s noted Great Firewall, it is also a product designed by the Falun Gong and funded by the U.S. government.
Note 1: Searching for the phrase “无界网络” is not only blocked on Weibo, but it will also cause your connection to the site to break, the only such phrase discovered thus far to cause such an action (searching for blogspot.com on Baidu does something similar). A user is locked out of Weibo for several minutes before they are allowed to reconnect.
Note 2: There have been allegations that Ultrasurf is possibly malware, or at the very least exhibits behavior that appears suspicious, a claim that is difficult to dispel because the source code has not been released (in order to prevent Chinese analysis), though others vigorously defend the software. As mentioned, recently it has been funded in part by the U.S. government and the Berkman Center at Harvard lauded its performance in 2007 (2010 report).
