They call it the Great Firewall of China - an elaborate system of software filters that dictates what internet content China's 100 million web users are allowed to access.

The Chinese Government uses it to weed out all the things it doesn't want its citizens reading about, listening to or watching.

As well as criticism of its policies and administration, the Government is adverse to "sex, violence and feudal superstitions", according to the official Chinese news agency, Xinhua. It's not keen on gambling either.

It means that if you are in China, there's no point Googling Tiananmen Square, Dalai Lama or anything triple-x in nature on Google.cn. You won't get the whole story.

Pen columns in the West about China's meddling in Tibet and it's unlikely anyone in China will ever get to read them.

We were shocked that an Asian broadcast of Prime Minister Helen Clark's interview on CNN was edited when she strayed onto the touchy subject of China's human rights record. The Chinese live with such interruptions every day.

As Clark pointed out: "Obviously China is not a democracy, and it is governed in a way that would not be acceptable in a Western democracy."

And neither is the internet governed in China as it would be in a Western democracy. According to a report released in April by the Open Net Initiative (http:/www.opennetinitiative.net/) China has the "most sophisticated internet-filtering regime" in the world and has increased censorship since the last report in 2002. China's internet monitoring taskforce numbers 30,000 people.

It's a different world, one where fear of defaming someone or embarrassing yourself are not the things holding you back from publishing your opinions on the internet, but the real risk of going to prison.

China's legacy of public infrastructure ownership means the Government has direct access to the fibre-optic networks that carry internet traffic in and out of the country.

They identify "objectionable" content by internet protocol (IP) address, searches for keywords and by domain name. I doubt that the Friends of Falun Gong website (www.fofg.org) gets any hits from China.

It's not just the big search engines and websites such as Sohu.com, Netease.com and Baidu.com that are monitored and filtered. Email messages, instant messenger conversations, weblog postings and bulletin board messages also pass through the filter. T he Chinese understand technology, so the filtering is very good - it's done in real time and is selective in nature. Sections of a website will often be blocked rather than the entire site.

If the censorship wasn't bad enough already, a new edict handed down from China's Ministry of Information Industry - at www.cnii.com.cn/ecnii - threatens to limit free speech even further.

Every Chinese website and weblog has to be registered with the Government by the end of the month to avoid large fines and having their websites blocked.

It means that the Government will know exactly who is operating each website and whose door to kick in if something disagreeable is published.

This regressive move has infuriated free-speech advocates. The organisation Reporters Without Borders (www.rsf.org) has been particularly critical of the Government's moves to tighten the thumbscrews, worried that the registration rules will force the more vocal bloggers to host their websites overseas and therefore not be available to Chinese surfing the web in their home country.

But I don't think China's stranglehold on free speech can last much longer. That's because two things are becoming more readily available in the country: technology and money.

There are 43 million broadband users in China and 330 million cellphone users.

As new technologies are adopted, including satellite broadband and 3G mobile services, it will become harder to ringfence the Chinese internet.

An expanding middle-class is also demanding more services, including e-commerce. And they want the services we in the West enjoy. Yahoo, Amazon, eBay and Google, the powerhouses of the internet, are all looking to China for growth.

Any company of any size wants to do business in China and to accommodate them, a freer internet environment will have to operate.

At the same time, Chinese corporations are investing heavily in other parts of the world as they take advantage of the forces of globalisation. It's only a matter of time before they push their agenda for change back home.

Which is why China's internet censorship regime is likely to be quietly dismantled over the next few years. Economic necessity will dictate it.

In the meantime, activists develop ways of circumventing the system.

Free-speech advocates Peacefire (www.peacefire.org) are offering their Circumventor software, which allows content to be sent to someone in China with a URL that is unrelated to the source.

The Electronic Frontier Foundation has an initiative under way called "Tor" http://tor.eff.org/, which is designed to make web activity anonymous.

"Communications are bounced around a distributed network of servers, called onion routers, instead of taking a direct route from source to destination," says the foundation.

The most worrying thing about Chinese internet censorship is the level of self-censorship it has developed among the Chinese. People know where the line is and are scared to cross it. That's because China has a dodgy track record on human rights, as this report from the US Government points out: www.state.gov/g/drl/rls/hrrpt/2004/41640.htm.

Executions are numerous and thousands of dissidents are jailed for criticising the Government. In that environment, speaking your mind is incredibly risky.

You can't blame the Chinese who opt for a safer, filtered view of the world.