'Great Firewall of China' urges self-censorship

The Chinese government's "Great Firewall of China," used to filter objectionable content from reaching users via the Internet, is actually a "panopticon," or an area where everything is visible, and not a true firewall at all, according to university researchers. Instead, the government uses the pretext of watching people to encourage them to censor themselves because they think they're being watched, the researchers from the University of California at Davis and the University of New Mexico said.

"Many countries carry out some form of Internet censorship. Most rely on systems that block specific Web sites or Web addresses," said researcher Earl Barr, a graduate student in computer science at UC Davis, in a statement. "China takes a different approach by filtering Web content for specific keywords and selectively blocking Web pages."

Using a system discovered in 2006 by researchers at the University of Cambridge in England, Barr, along with Jed Crandall and several other researchers, sent messages containing a variety of potentially objectionable words to Internet addresses in China.

If the government's censorship system was a true firewall, the words would have been blocked at the border with the rest of the Internet, Barr said. However, he said, the researchers discovered that some messages passed through several routers before they were blocked.

"A firewall would also block all mentions of a banned word or phrase, but banned words reached their destinations on about 28% of the tested paths," according to the statement. "Filtering was particularly erratic at times of heavy Internet use."

The researchers said the words they used were not selected at random. Instead they took individual words from the Chinese version of Wikipedia, then used a mathematical technique called latent semantic analysis to figure out the relationships between different words. The researchers said if they found that one of the words was censored in China, they then looked up other closely related words that were also likely to be blocked.

The words the researchers tested and found were banned in China included references to the Falun Gong movement, the protest movements of 1989, Nazi Germany and other historical events, plus ideas about democracy and political protest.

"Imagine you want to remove the history of the Wounded Knee massacre from the Library of Congress," said Crandall, a recent UC Davis graduate who is now an assistant professor of computer science at the University of New Mexico School of Engineering. "You could remove Bury My Heart at Wounded Knee and a few other selected books, or you could remove every book in the entire library that contains the [key]word 'massacre.'"

The researchers said China's Internet censorship was based on that type of keyword filtering. However, because keyword filtering screens ideas and not specific Web sites, it stops people from using proxy servers or "mirror" Web sites to avoid censorship. But since it's not effective all the time, it most likely causes users to censor themselves, Barr said.

"When users within China see that certain words, ideas and concepts are blocked most of the time, they might assume that they should avoid those topics," he said.