Chinese censors are actively targeting social media to quash discussion of banned topics, suggests research.
The US study gives the most in-depth look at the extent of China's policing of discussions on microblogging sites.
Analysis of almost 60 million messages from China's equivalent of Twitter suggested which topics were banned.
It also revealed that China tuned its censoring activity to be more aggressive in places where political unrest was high.
The study, reported in New Scientist, by David Bamman, Brendan O'Connor and Prof Noah Smith from the Language Technologies Institute at Carnegie Mellon analysed short messages sent via the Sina Weibo service.