•Demanding self-censorship. Chinese authorities hold commercial websites responsible for what appears on them. In Beijing — where Internet controls are strictest — authorities issue orders to website managers through cellphone text messages and demand that they comply within 30 minutes, according to a report last fall by Reporters Without Borders.
When the Internet portal Sina altered the headline of a state media report on the economy, the government accused it of "inciting violence" and excluded it from interviews with important officials for a month. The website NetEase fired two editors after they published a 2006 poll showing that 64% of 10,000 participants would not want to be reborn as Chinese.
•Issuing propaganda. Authorities in the southern boomtown of Shenzhen created two cute cartoon cybercops — the male Jingjing and the female Chacha — that pop up on websites to remind Internet users they're being watched. The Beijing Youth Daily newspaper quoted a security official admitting that the big-eyed cartoon duo were designed "to intimidate."
Chinese officials also order websites to reprint official propaganda such as a report encouraging Internet users to abide by online etiquette.
•Getting outside help. China has policed the Internet with assistance from U.S. firms. Cisco Systems, for instance, supplied the original routers China used to monitor Internet traffic. (Cisco has said it didn't tailor its equipment for the Chinese market.)
Google created a censored search engine for China. Outside China, users who search Google Images for "Tiananmen Square" get pictures from the 1989 pro-democracy protests that ended in a crackdown that left hundreds dead — and included the iconic photograph of a lone man staring down a line of Chinese tanks. Inside China, users get only tourist images of Tiananmen Square and the Forbidden City across the street.
Yahoo turned over e-mail that authorities used to jail a Chinese journalist who leaked information about China's attempts to censor coverage of the anniversary of the Tiananmen crackdown.. (The companies say they had to comply with Chinese law.)
Despite China's strategies, sophisticated Internet users in the country "can pretty much get as much information as (they) want," says Jeremy Goldkorn, the Beijing-based editor of the China media website danwei.org. "But what (the government does) is make it difficult, so the ordinary person is not going to bother."
In 2002, Xia formed a company — Dynamic Internet Technology — to wage cyberwar on the Chinese regime. He created Freegate, a software program that finds holes in the firewall and takes Chinese Internet users to banned websites, undetected.
Xia also sends millions of e-mail messages into China for customers such as Voice of America and the activist group Human Rights in China. The e-mails contain links to forbidden sites at an ever-changing list of temporary Internet addresses, part of an effort to stay a step ahead of Chinese censors.
Traffic on his network of "proxy" websites picked up in February, when heavy snows blocked traffic and shut train service in southern China, Xia says.
The Chinese government was reluctant to admit anything had gone wrong, so frustrated travelers turned to renegade websites to get practical information on weather conditions and rail service.