When Lu Jing sends e-mails about Japan, he cannot write the word he uses in normal conversation, xiao riben [little Japan] because the word and the message it is in will be deleted in less than a minute. So he writes 'xiao J' instead. It is a small example of the world's most sophisticated internet monitoring system set up by the central government to control what its citizens can and cannot see and say on the internet. It involves state-of-the-art equipment and an army of tens of thousands of people, including secret police, uniformed police, officials at universities and the Cultural Department, staff at service providers and unpaid volunteers who monitor online chat rooms. For the majority of Chinese 'internauts', the system works - they are only able to reach sites to which the government gives them access and, mindful of what is allowed and not allowed, do not dare to send messages with content that might get them into trouble. It is only a small minority of students - people with a high level of computer skill and the audacious - who dare to look for proxy servers and overcome the obstacles. 'China operates the most extensive, technologically sophisticated and broad-reaching system of internet filtering in the world,' said a new report by a non-government organisation called OpenNet Initiative (ONI), a partnership between units of the University of Toronto, Harvard Law School and Cambridge University. 'Compared to similar efforts in other states, China's filtering regime is pervasive, sophisticated and effective,' the report said. 'It comprises multiple levels of legal regulation and technical control and numerous state agencies. This regime is buttressed by an equally complex series of laws and regulations that control the access to and publication of material online. 'Considering that China's growing internet population represents nearly half of all internet users worldwide and will soon overtake the US as the single largest national group of internet users, such extensive censorship should be of concern to all internet users worldwide. Its advanced filtering regime presents a model for other countries with similar interests in censorship to follow.' According to the most recent official figures, China has 94 million internet users, nearly half with broadband access. Other estimates put the total at 130 million users, including those who do not have a computer at home but access the internet from cyber cafes. Nearly 60 million unique internet protocol (IP) addresses have been assigned to computers in China. This filtering regime has developed to meet two contradictory objectives. One is to harness the internet as an essential tool in the country's drive to become a major power, such as promoting business and trade, educational and scientific exchanges and raising personal and company efficiency. The other is to extend on to the internet the tight controls on news and information the Communist Party has put in place since 1949. So it was no surprise that, in February 1994, one year before the internet became commercially available to Chinese users, the State Council entrusted the Ministry of Public Security with overall responsibility for the supervision of the internet. A 1996 regulation required all subscribers to register with the local police within 30 days of signing up with an internet service provider. Police units were set up to investigate alleged violations. Internet cafes are required, at their own expense, to install equipment that records the identity of each user and what sites they visit. These regulations cover external use of the internet. A further set controls the content. The first major directive, State Council Order 292, promulgated in September 2000, says that content providers are responsible for the legality of their services, and sets out nine categories of information that cannot be published or disseminated. The ONI conducted widespread testing of subjects sensitive to China. 'China's blocking of sensitive content, such as the banned Falun Gong movement, Tibetan independence or Taiwan, is extensive,' it said. 'The state's filtering is not perfect - we were able to circumvent keyword detection for blog posts and obtained filtered material at alternative locations - but it is nonetheless thorough. The filtering regime is one of the most sophisticated in its ability to detect and prevent access.' The report also found extensive blocking of material on: the 1989 military crackdown; human rights in China and pro-democracy websites; sites operated by the Taiwan government and organisations promoting Taiwan independence; discussions on the Dalai Lama and the dispute over Tibet; and late Communist Party general secretary Zhao Ziyang. BBC and Voice of America sites were often blocked. In the past year, the government has intensified its efforts to control the opinions of the estimated 600,000 bloggers, who post content ranging from diaries to political commentary. In August last year, Chinese hackers found a list of 987 sensitive keywords which set off filtering software, including independence movements, the Tiananmen crackdown, Falun Gong and the names of Communist Party leaders. Former president Jiang Zemin is a favourite butt of jokes, because of his large belly, his love of poetry and singing, and the mistresses he is alleged to have. 'When I write about Jiang, I cannot write his name in Chinese or English,' said Lu Jing. 'I write 'Old J' or 'xxx' and my friends know who I mean. Similarly, I cannot write Chen Yonglin [the diplomat who sought asylum in Australia] in Chinese or English. I say 'a senior official in Australia'.' 'China makes a systematic, comprehensive and frequently successful effort to limit the ability of its citizens to access and post online content the state considers sensitive,' the ONI report said. 'The state employs a sophisticated infrastructure that filters content at multiple levels and tolerates overblocking as the price of preventing access to prohibited sites.' China's advanced internet control system uses equipment from a number of foreign companies, including Cisco Systems, Nortel Networks, Sun Microsystems, Microsoft and 3COM. Human rights organisations have charged these firms with actively assisting China in developing censorship and surveillance systems. They respond that they cannot tell their customers how to use the goods they sell to them.