BEIJING — China has refined a unique model of policing the Internet in which private business self-censors nearly as much as state censors themselves.
The largest private Chinese Internet companies now employ their own teams of monitors to enforce often-vague state guidelines about what's permitted. Censors are quick to delete posts they consider touchy, and commercial Internet portals and blog-hosting sites enforce controls with vigor, lest their licenses get pulled.
The result is probably the most precise, robust and sophisticated Internet censorship system in the world. The monitoring has intensified as leaders of the ruling Communist party prepare to descend on Beijing for a major conference.
"They say, 'This is what we have to do. If we don't do this, our business will get shut down,'" said Rebecca MacKinnon, a former CNN correspondent who's now an assistant professor of new media at Hong Kong University.
Some of the businesses, such as sina.com, sohu.com and baidu.com, are listed on overseas stock markets and carry multibillion-dollar valuations on their stock prices. Any conflict with the government over content could frighten investors and send stock prices tumbling.
Foreign Internet and high-technology companies also have been accused of collaborating with China's efforts to maintain what wags dub the Great Firewall, though to a far less extent than domestic companies do.
Google offers Chinese users a censored version of its search engine, and Microsoft acknowledges that it blocks Chinese-language blogs that contain forbidden language. Such language is said to include phrases such as "human rights" and "Taiwan independence." Cisco, a maker of telecommunications equipment that is the backbone of the Internet, sells China technology used in Internet surveillance. Skype collaborates with a Chinese partner that filters text chat on mobile phones. Yahoo has come under the greatest fire for providing Chinese authorities with personal information about Chinese subscribers, who were later sentenced to jail. Yahoo has said it had little choice but to comply with a legal order from the Chinese government.
The Chinese government wields the guiding hand in Internet censorship, but it ebbs and flows with the sensitivities of the calendar. Recently, pressure has spiked in the run-up to the 17th party congress starting Oct. 15, during which the Communist Party taps China's future leaders and sets the political agenda for the next five years.
"In the past couple of weeks, everybody's getting the message from on high that the discussion of the 17th party congress is one of those things that needs to be policed and taken down . . . so that there's no criticism," MacKinnon said.
Authorities have flexed their muscles to get that point across. In late August, authorities began switching off entire Internet data centers, which house thousands of servers, blacking out large numbers of domestic Web sites and coinciding with a general network slowdown. Many have since returned to operation.
The clampdown was done in the name of fighting "illegal" Web sites, namely those that hosted pornography or were unregistered. But analysts said the broader aim was to ensure that private Internet businesses hewed closely to efforts to keep anti-government sentiment from seeping online.
"It's a pretty widespread crackdown," said Andrew Lih, a former academic at Columbia University who researches new media in Beijing. "It's as great as it ever has been."
Last month, the English-language Shanghai Daily said authorities had blocked access to 18,401 "illegal" Web sites since April.
In an unusual partnership with state censors that began Sept. 1, 13 private Internet portals in Beijing began letting "pop-ups" of two cartoon policemen appear on users' screens every 30 minutes to remind them of lawful behavior.
Lih said China's Internet regulations are deliberately vague, leaving private Internet companies vulnerable and with hair-trigger fingers to delete anything sensitive.
"If you can keep it ambiguous, then the companies stay conservative to make sure they don't cross a mythical line," Lih said. "This is something that works even better than having hard guidelines."
MacKinnon said the unplugging of the Internet data centers was a sign that authorities want private firms hosting Web sites to exercise a firmer hand.
A senior executive with a large Chinese Internet company, who spoke on condition of anonymity to safeguard her job, said the portal employed teams of monitors who receive guidance from government censors "nearly every hour."
The South China Morning Post, a Hong Kong newspaper, reported in March that sohu.com deletes some 100,000 messages to its site each day, indicating the scale of private involvement in censorship.
President Hu Jintao exhorted Internet monitors last January to "raise the level of guidance online" and to "purify the Internet environment."
While the majority of China's 162 million Internet users are largely interested in gaming and popular culture, rarely if ever visiting overseas Web sites, prominent bloggers have amplified public concerns on social issues and even gained power to set agenda, drawing millions of readers. Their interactive blogs, along with the text-message capabilities of China's 487 mobile phones users, leave authorities worried about the self-organizing capabilities of society. In response, some Web sites have limited, or even eliminated, viewer responses to blogs and have shut down open forums.
"Many of my friends have closed the comment feature of their personal blog(s)," Shanghai blogger Wang Jianshuo wrote last month, voicing frustration at the clampdown.
"If you ask me how I feel, as a blogger in China, I would say I am very, very, very frustrated about it," he wrote.
Exactly which departments or bureaus are behind the latest crackdown is unclear. As many as a dozen security, information and propaganda bureaus have oversight of the Internet, and municipalities also have enforcement and censorship authority.
"It is very complex to define who 'they' are," said Isaac Mao, an Internet analyst in China, adding that the clampdown is "definitely related to the coming party congress."
By setting up complaint hot lines about "illegal" Internet activity, authorities want to harness individuals to cleanse the Web. Volunteers at university campuses, known as "little sisters," patrol online forums and steer debate in certain approved directions.
Resorting to creativity to get around the clampdown, Internet users employ homonyms of Chinese characters to touch on sensitive issues, such as President Hu's campaign to build a "harmonious" society. Since the Chinese word for "harmonious" has the same sound as "river crab," the Internet now has tens of thousands of sarcastic references to river crabs.
(McClatchy special correspondent Fan Di contributed to this story.)