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Routed out: China’s efforts to block access to Tor, a tool for anonymous Web surfing, kicked in on September 25. This graphic shows the number of real-time requests from within China for Tor’s directory–an indicator of Tor usage.

The events of late September showed that China is stepping up its blocking efforts, said Wendy Seltzer, a law professor and research fellow at the University of Colorado who founded and developed the Chilling Effects Clearinghouse, a project to fight unjustified legal threats to the Internet. “Watching China step up blocking around nationally significant events shows the degree of control they are trying to exercise,” added Seltzer, who is also an uncompensated member of Tor’s board. “The experience helped to validate Tor’s strategy of having lots of defenses in queue.”

Tor is now working out ways to more efficiently and rapidly disseminate bridge addresses in the future, including via Twitter. “The issue is, obviously, that the Chinese government could also use Twitter to receive the bridges, and block those, too,” adds Lewman. He is working on ways to time responses to such requests to make things more difficult for the government to block. “Writing the code is the easy part. The logic behind it–that’s the hard part.”

In 2006, the OpenNet Initiative–a research collaboration among several universities–reported filtering in 25 of 46 nations tested. In another forthcoming study, the OpenNet Initiative will report that these efforts are expanding, says Ronald Deibert, a political scientist and director of the Citizen Lab at the University of Toronto, one of the participating universities.

The trend of time-sensitive national crackdowns has increased in the past four years, Deibert says. “Often governments block access to information not as static or passive filtering walls, but rather at key moments in time when the information has most value, such as during public demonstrations, key historical events, or election periods,” notably including, in recent months, the disputed Iranian election, he adds.

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Credits: Technology Review , Tor Project

Tagged: Communications, Web, security, Internet, China, anonymity, online tools, Tor, IP address

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