Even so, Chinese authorities constantly are finding new ways to plug the holes Freegate finds or to otherwise stymie Xia's efforts. He figures has upgraded Freegate 20 times. "We're gradually getting faster and faster" at fixing problems with the software when Chinese users report them, he says.
Chinese Internet users also use decidedly low-tech methods to evade official attempts to censor their e-mail or online commentary.
They will, for instance, try to throw off the cybercops by inserting spaces or punctuation marks between characters — much as spammers in the USA try to beat e-mail filters by offering "Free V i@gra!"
The authorities try to update their list of banned terms — now running into the hundreds — to include those with creative punctuation.
Rebecca MacKinnon, former Beijing bureau chief for CNN, spotted the way some cheeky Chinese Internet users stayed ahead of the censors. Whenever their edgy comments were purged from a website, they'd joke online that they'd "been harmonized" — a sarcastic reference to Chinese President Hu Jintao's calls for a "harmonious society." Soon, the censors caught on and added "harmonized" to the blacklist.
The Chinese term for "harmonized" is he xie— which sounds the same as the Chinese term for "river crabs" but with a slightly different intonation. Now, Chinese online chatter frequently includes references to river crabs — the latest code for censorship, says MacKinnon, who studies the Chinese Internet at the University of Hong Kong.
Xia says he's confident the "hacktivists" can win their cat-and-mouse game with the Chinese authorities. After all, he says, the Chinese zodiac favors rodents in 2008: "It's the Year of the Rat."
Contributing: Calum MacLeod in Beijing