Internet users are being urged to stand up for online freedoms by backing a new campaign launched by human rights group Amnesty International.
Yahoo is accused of helping China identify dissidents
Amnesty is celebrating 45 years of activism by highlighting governments using the net to suppress dissent.
The campaign will highlight abuses of rights the net is used for, and push for the release of those jailed for speaking out online.
It will also name hi-tech firms aiding governments that limit online protests.
Called Irrepressible.info, the campaign will revolve around a website with the same name. While the human rights group has run separate campaigns about web repression and the jailing of net dissidents before now, Irrepressible.info will bring them all together.
It aims to throw light on the many different ways that the freedom to use the net is limited by governments.
For instance, said a spokesman for Amnesty, around the globe net cafes are being closed down, home PCs are being confiscated, chat in discussion forums is being watched and blogs are being censored or removed.
"The internet has become a new frontier in the struggle for human rights," said Kate Allen, UK director of Amnesty International.
"Its potential to empower and educate, to allow people to share and mobilise opinion has led to government crackdowns."
Ms Allen added that there were growing numbers of cases in which those who have turned to the net to discuss change or protest about government policies have been jailed for what they said.
For instance, she said, Chinese journalist Shi Tao is serving a 10-year jail sentence for sending an e-mail overseas which detailed the restrictions the Chinese government wanted to impose on papers writing about the 15th anniversary of the Tiananmen Square massacre.
Hi-tech firm Yahoo helped identify the journalist via his e-mail account. Amnesty is calling for the jailed journalist to be released immediately.
However Mary Osako, a spokeswoman for Yahoo, said the case was "distressing" to the firm.
"We condemn punishment of any activity internationally recognised as free expression, whether that punishment takes place in China or anywhere else in the world," she said.
She added the company had received "a valid and legal demand" for information and responded to it as required by the law.
She went on: "The choice in China or other countries is not whether to comply with law enforcement demands for information. Rather, the choice is whether or not to remain in a country.
"We balance the requirement to comply with laws that are not necessarily consistent with our own values against our strong belief that active involvement in China contributes to the continued modernization of the country - as well as a benefit to Chinese citizens - through the advancement of communications, commerce and access to information."
Profit and principles
The Amnesty campaign will seek to get net users to sign a pledge that opposes repressive use of the net. The pledges will be collated and presented to a meeting of the UN's Internet Governance Forum that is due to meet in Athens in November 2006.
Amnesty wants to get people using an icon in e-mail signatures or on websites that contains text from censored sites.
The group also wants to run an e-mail campaign to target companies to stop putting "profit before principles" and respect human rights everywhere they operate.
Reports will be prepared on those countries that place restrictions on what can be said online or use it to keep an eye on those expressing discontent.
"Irrepressible.info will harness the power of the internet and of individuals to oppose repression and stand up for free speech," said Ms Allen.