December 04, 2006 - Cat and mouse, on the web


Technology Quarterly
Techniques to evade censorship of Internet traffic are improving, to the chagrin of authoritarian regimes

For a website lashed together in a week by a college student, is not to be sniffed at. Alexander Pircher, a computer-science student in Darmstadt, Germany, created the site in 1997. Users simply type a web address into a box on the Anonymouse home page and click a button, and the Anonymouse server (rather than the user's own computer) fetches the page and displays it. To many people this might seem pointless: rerouting data through another server makes for slower surfing, fonts and graphics are sometimes slightly skewed and video may not work properly.

But for many others the manoeuvre is anything but pointless, for this redirection allows them to surf the web anonymously. It enables people living under repressive regimes to visit censored websites because, technically speaking, they are only visiting More than 3m people access the web through every day and Mr Pircher, who now upgrades his software with help from friends, says he receives plenty of thank-you messages from censorship-dodgers in countries like Cuba, Iran, North Korea and Saudi Arabia. “We're bringing people the Universal Declaration of Human Rights,” he says, referring to Article 19 of the United Nations document, which says freedom of information is a fundamental right. is not alone. It is part of a large and growing constellation of similar computer servers, known as proxies, put online for the most part by activists living in free countries. These proxy servers play a central role in the global struggle to outsmart censors working to protect undemocratic regimes from political and social dissent. Mokhtar Yahyaoui, a lawyer in Tunisia, says that in his country proxies “are pretty much the only way to get information that's not official government information”.

But censors have an effective countermeasure. Once they identify a proxy, they can block access to it, just as they block access to other sites. The difficult part is finding the proxies, but the software used by censors, called censorware, is getting better at it. China's censors are leading the way. The estimated 30,000 government censors behind the world's most elaborate censorship programme—known as the Great Firewall of China by detractors, and as the Golden Shield by the Communist Party—work hard to hunt down proxies and prevent them from relaying data into the country.

The anti-censorship community is developing new ways to evade censors in response. For example, when China blocks a proxy ('s fate in that country), internet users can find a replacement by consulting a growing number of websites that compile and post lists of working proxies. E-mailed newsletters that provide links to proxy servers are also available. Some anti-censorship organisations spread the word via instant-messaging services: people looking for a proxy simply send an instant message to one of these groups and immediately receive an automated reply with a recently updated list of proxies.

These methods work because it usually takes censors a little while to identify and block new proxies. China's censors are probably the fastest to react, but even then some proxies survive for a week or more, in part because the firewall is maintained by a complex network of private and state-controlled telecommunications operators, and national, provincial and municipal government agencies that don't always act in concert. Lesser-known proxies handling small amounts of traffic generally go undetected the longest, sometimes for months. “It's a game called cat and rat,” says Mao Xianghui, a partner in an investment firm in Shanghai. His blog provided advice on using proxies to sidestep censorship, until authorities shut it down last year.

An American non-profit group called Tor operates one of the most robust anti-censorship systems. Using money provided by America's Naval Research Laboratory and the Electronic Frontier Foundation, a free-speech advocacy group, Tor developed free software that can be downloaded from many websites. The software works in conjunction with a web browser (the developers recommend Firefox) to encrypt traffic and route it through three proxy servers chosen at random from a network of around 1,000 proxies run by Tor volunteers worldwide. This makes it difficult for censors to determine what information is being sent, where it came from, and who received it. A Tor spokeswoman says many human-rights groups advise their activists in authoritarian countries to use the software to avoid government snooping.

This is not the only tool available to activists. In June of last year Huang Qi, an outspoken human-rights activist from Chengdu, China, was released after serving five years in prison on charges of subversion. He promptly downloaded a free “circumvention” programme that had been developed during his detention. Now, when Mr Huang opens his browser, the software, called Wujie, automatically searches the internet until it locates a functioning proxy server through which to connect. “It opens the doors to the world,” he says.Censorship firewalls rely heavily on keyword-blocking software, which can catch and block e-mails and instant messages containing words and phrases deemed dangerous. Bill Xia, a Chinese dissident living in North Carolina, employs a number of tricks to sneak words past censors. He is the founder of Dynamic Internet Technology, a company paid by the American government's International Broadcasting Bureau to e-mail more than 2m pro-democracy Voice of America and Radio Free Asia newsletters into China and Vietnam every day. To foil keyword filters, Mr Xia replaces sensitive words such as “freedom” and “elections” with uncommon or approximate synonyms, or descriptive phrases. He inserts random characters, such as asterisks, between Vietnamese letters or the ideograms that make up Chinese words. Other techniques include writing words in a mixture of several fonts, replacing parts of words with syllables that sound similar, and replacing words with pictures of those words.

Employing such ruses makes for tedious writing and choppy reading. And having to bother with proxy servers to surf the web can be a hassle. But for those who are victims of censorship, the increasingly elaborate efforts required to outmanoeuvre censors are liberating, empowering and well worth the effort.

© The Economist Newspaper Limited 2006