The trial in China of a man accused of using the Internet to try to overthrow the government represents the latest attempt by states to try to control use of the medium.

Asian countries in particular have viewed the Internet as a threat to their national security, with its ability to organise protest movements by linking together dissidents at home and abroad.

A leading Internet campaigner once said that the worldwide network of computers interprets censorship as damage and routes around it.

This is the problem for governments trying to control the spread of information they feel undermines them.

There are many ways of getting it out over the Internet. China has tried to control access to Websites outside the country by routing Internet access through government controlled computers in Beijing, Shenzhen and Shanghai.

The state is controlling access to information

This way it can block access to sites it feels are subversive. But users can get around this by dialling an Internet service provider outside the country.

The current trial concerns E-mail, which is harder to control than Websites. It is not easily monitored, can be sent anonymously and in a coded format which can be next to impossible to crack.

A powerful form of E-mail is a posting made to a news group - a kind of electronic bulletin board.

India blamed Pakistan for hacking into the army's Kashmir pages

In September, the Malaysian authorities put on trial four people accused of causing unrest after messages were posted reporting possible riots.

Perhaps the cleverest and most effective way of showing dissent on the Internet is to break into official government Websites, as a new generation of political hackers are finding out.