China's Internet censorship world's most extensive

China has the most extensive Internet censorship in the world, regularly denying users access to 19,000 Web sites that the government deems threatening, a study by Harvard Law School researchers has found.

The study, which tested access from multiple points in China over six months, found that Beijing blocked thousands of the most popular news, political and religious sites, along with selected entertainment and educational destinations. The researchers said censors sometimes punished people who sought forbidden information by temporarily making it hard for them to gain any access to the Internet.

Internet sites on democracy, Tibet and Taiwan were among Web destinations most frequently blocked by the Chinese government. Other sites blocked included those on health, education, news, entertainment, religion and pornography.

Ben Edelman, a Berkman researcher, and Jonathan Zittrain, the center's co-director, checked more than 204,000 Web sites, identified in part using search engines Google and Yahoo!, and found more than 19,000 inaccessible at least some of the time.

The top 10 Google results using the key words ``Tibet,'' ``Taiwan China'' and ``equality'' were all blocked, as were eight of the top 10 results using ``democracy China'' and ``dissident China.''

Seven of the top 10 were blocked using ``Taiwan'' alone and ``revolution.''

The country often blocks an entire Web site, even if only parts of the site contain sensitive information, Edelman said.

Chinese users cannot often reach the sites run by Amnesty International or Human Rights Watch. China also does not allow users to connect to major Western religious sites.

News media sites are also often blocked. Among those users had trouble reaching in the test period were National Public Radio, The Los Angeles Times, The Washington Post and Time magazine.

Defying predictions that the Internet was inherently too diverse and malleable for state control, China has denied a vast majority of its 46 million Internet users access to information that it feels could weaken its authoritarian power.

"If the purpose of such filtering is to influence what the average Chinese Internet user sees, success could be within grasp," said Jonathan Zittrain, a professor at the law school and a co-author of the study.