A new report by OpenNet Initiative examines the Chinese government’s filtering of web content:
The OpenNet Initiative tested China’s Internet filtering of web content, blog postings, and e-mail correspondences. Our testing found efforts to prevent access to a wide range of sensitive materials, from pornography to religious material to political dissent. Unlike the filtering systems in many other countries, China’s filtering regime appears to be carried out at various control points and also to be changing over time. China operates the most extensive, technologically sophisticated, and broad-reaching system of Internet filtering in the world.
See also “China uses ever more effective Net filters” from AP (via IHT).