BBC: Behind China's internet Red Firewall

But it has worked hard to muzzle the web as a forum for free information and discussion.

One of the ways it does this is by blocking access to foreign websites such as Google by what has been called the Great Red Firewall.

The main contact points connecting China's internet with the worldwide system consist of nine Internet Access Providers that control the physical lines to the outside world.

Traffic over the lines can be restricted through the use of internet filters, software that can deny access to specific internet addresses.

Filtered content

Beijing routinely uses filters to block access to sites run by the banned spiritual movement Falun Gong, human rights groups and some foreign news organisations.

Internet activity is closely monitored But Chinese surfers often use proxy servers - websites abroad that let surfers reach blocked sites - to evade the Great Red Firewall.

Such techniques are routinely posted online or exchanged in chat rooms.

But China's 45 million internet users face considerable penalties if they are found looking at banned sites.

According to human rights activists, dozens of people have been arrested for their online activities on subversion charges.

Legal web

Since 1995, when Chinese authorities started allowing commercial internet accounts, at least 60 laws have been passed aimed at controlling content online.

Among the measures, all internet users have to register with a police bureau in their neighbourhood within 30 days of opening a web account.

Human rights activists say more than 30,000 people are employed to keep an eye on websites, chat rooms and private e-mail messages.

A fire in a Beijing net cafe in June that killed 25 people led to a broader government crackdown. Since then, 150,000 unlicensed internet cafes nationwide have been closed.

Those remaining have had to install software that prevents access to up to 500,000 banned sites with pornographic or so-called subversive content.

One programme, the Filter King, not only records attempted hits on banned sites, but is also said to send daily reports to local police net units.

Self-control

There is also a degree of self-censorship, as Chinese internet portals have been warned that they will be held responsible for sites they host.

One of the main portals, Sohu.com, has appointed censors to monitor the chat rooms and delete unsuitable material, say human rights activists.

In internet cafes, managers are reported to have people who patrol the monitors checking what material appears on the screen.

A Chinese internet industry body recently unveiled what it called the Public Pledge on Self-Discipline for the China Internet Industry.

The pledge has been signed by 130 major web portals, including the search engine Yahoo.

The signatories agree not to post information that will "jeopardise state security and disrupt social stability".