social media censorship offers clues to china's plans...,

technologyreview | In February last year, political scandal rocked China when the fast-rising politician Bo Xilai suddenly demoted his top lieutenant, who then accused his boss of murder, triggering Bo's political downfall.

Gary King, a researcher at Harvard University, believes software he developed to monitor government censorship on multiple Chinese social media sites picked up hints days earlier that a major political event was about to occur.

Five days before Bo demoted his advisor, the Harvard software registered the start of a steady climb in the proportion of posts blocked by censors, a trend that lasted for several days. King says he has noticed similar patterns several times in advance of major political news events in the country. "We have examples where it's perfectly clear what the Chinese government is about to do," he says. "It conveys way more about the Chinese government's intents and actions than anything before."

King has seen dissidents' names suddenly begin to be censored, days before they are arrested. A jump in the overall censorship rate, like the one that foreshadowed Bo's fall, also presaged the arrest of artist Ai Weiwei in 2011. The rate declined in the days before the Chinese government announced a surprise peace agreement with Vietnam in June 2011, defusing a dispute over oil rights in the South China Sea. King suspects those patterns show that censors are being used as a tool to dampen and shape the public response to forthcoming news. That tallies with his other findings that censors focus on messages encouraging collective action rather than just blocking all negative comments.

China's social media censorship is less well known, and less understood, than the system known as the Great Firewall, which blocks access to foreign sites, including Facebook and Wikipedia, from inside the country. But social media censoring is arguably as important to the country's efforts to control online speech. Social media is attractive in a country where conventional media is tightly controlled, and the Great Firewall directs that interest toward sites under government direction.

Studies like King's tracking which posts disappear from social media services in China have now begun to reveal how the country's censorship works. They paint a picture of a sophisticated, efficient operation that can be carefully deployed to steer the nation's online conversation.

The most popular social media services in China are microblog networks, or "weibos," roughly equivalent to Twitter and used by an estimated 270 million people, according to government figures. In China, all microblog service providers must establish an internal censorship team, which takes directions from the government on filtering sensitive posts. Sina Weibo and Tencent Weibo between them claim the majority of active users, and are said to have censorship teams as large as 1,000 people.

Those teams can act fast, as a study of 2.38 million posts on Sina Weibo (12 percent were censored) showed last year. "It's minutes or hours, not days," says Jed Crandall, an assistant professor at University of New Mexico, who took part in research with colleagues from Rice University and Bowdoin College. Previous studies had only checked for deleted posts at intervals of a day or more, says Crandall, who concludes that assumptions that social network censorship was largely manual were incorrect. "There must be some automation tools that would help them, or they wouldn't be able to do the rate that we observed."

Crandall has also uncovered evidence of how Chinese censorship is used to steer the direction of public conversation rather than just being used to block out sensitive topics for good. His software saw censors successfully dampen the online outcry after a major train crash in July 2011 before carefully relenting once politicians had managed to shift public chatter onto more favorable terms. "It demonstrates the kind of PR that the censors are trying to pull off," says Crandall. "They delay the discussion until the news cycle changes—when the conversation changes to a favorable one, people can talk all they want."