How does it works? – Great Firewall of China
One part of this system is known outside China as the Great Firewall of China (in reference both to its role as a network firewall and to the ancient Great Wall of China). The system blocks content by preventing IP addresses from being routed through and consists of standard firewall and proxy servers at the Internet gateways. The government does not appear to be systematically examining Internet content, as this appears to be technically impractical.
This firewall is largely ineffective at preventing the flow of information and is rather easily circumvented by determined parties, most simply by using the cache for Google but also by using proxy servers outside the firewall.
Research into the Chinese Internet censorship has shown that blocked Web sites include:
- News from many foreign sources
- Information about Tibet independence
- Information about Falun Gong
- Some websites based in Taiwan
The banning appears mostly uncoordinated and ad-hoc with some sites being blocked while other similar sites are allowed. The blocks are often lifted for special occasions. One example was the New York Times which was unblocked when reporters in a private interview with Jiang Zemin specifically asked about the block and replied that he would look into the matter. During the APEC summit in Shanghai during 2001, normally-blocked CNN, NBC, and the Washington Post were suddenly accessible.
Chinese agencies frequently issue regulations about the Internet, but these are often not enforced or ignored. One major problem in enforcement is determining who has jurisdiction over the Internet, causing many bureaucratic turf battles within the Chinese government among various ministries and between central and local officials. The State Council Information Office has the mandate to regulate the Internet, but other security agencies in China have a say as well.
Some legal scholars have pointed that the frequency at which the Chinese government issues new regulations on the Internet is a symptom of their ineffectiveness because the new regulations never make reference to the previous set of regulations, which appear to have been forgotten.
Although blocking foreign sites has received much attention in the West, this is actually only part of the Chinese effort to censor the Internet. Much more effective is the ability to censor content providers within China, as the government can physically seize the Web site and the operators
Although the government does not have the physical resources to monitor all Internet chat rooms and forums, the threat of being shut down has caused internet content providers to have internal staff, who are colloquially known as “big mamas” who stop and remove forum comments which may be politically sensitive.
However, Internet content providers have adopted some counterstrategies. One is to go forth posting political sensitive stories and removing them only when the government complains. In the hours or days in which the story is available online, people read it, and by the time the story is taken down, the information is already in the public. One notable case in which this occurred was in response to a school explosion in 2001, when local officials tried to suppress the fact the explosion resulted from children illegally producing fireworks. By the time local officials forced the story to be removed from the Internet, news was disseminated widely.
Also, Internet content providers also often replace censored forum comments with white space which allows the reader to know that comments were taken down and to often guess what they were.
One controversial issue is whether Western companies should supply equipment to the Chinese government which aids in the blocking of sites. Some argue that it is wrong for companies to profit from censorship, while others argue that equipment being supplied is standard Internet infrastructure equipment and that providing this sort of equipment actually aids the flow of information. Without the equipment, the Chinese government would not develop the Internet at all. A similar dilemma faces Western content providers such as Yahoo! and AOL who must abide by Chinese government wishes, including having internal content monitors, to operate within China.
Sites that host software that can be used to circumvent the censorship, such as Freenet and Peek-a-Booty, are also banned. (For some time, this included the entire open source software repository at SourceForge, as it hosts the Freenet project, among thousands of others.)
Contrary to general Western perceptions of Internet cafes, they generally are not inhabited by political subversives, but are frequented by teenagers playing online games against each other or downloading MP3s. Ironically, most such cafes would be prosecuted in the West, not by the government, but by copyright holders, because they maintain extensive caches of illegally copied software and MP3s.
Source:
http://www.knowledgerush.com/kr/encyclopedia/Internet_censorship_in_China/
http://securityandthe.net/2009/05/03/borders-in-cyberspace/






