Almost 500 people have signed up on Facebook to attend the protest at Sydney's Town Hall, while more than 1000 will picket at Melbourne's State Library. Thousands more are listed as "maybe attending". Live trials of the controversial internet filters, which will block "illegal" content for all Australian internet users and "inappropriate" adult content on an opt-in basis, are slated to begin by Christmas, despite harsh opposition from the Greens, Opposition, the internet industry, some child welfare advocates, consumers and online rights groups.

Even NSW Young Labor has abandoned the Government's filtering plans, passing a motion last week rejecting the mandatory scheme and calling on Senator Conroy to adopt a voluntary opt-in system. Ed Coper, campaigns director at GetUp, said the response to the anti-censorship campaign had been "astronomical" and "quite unprecedented". Almost 80,000 people have signed GetUp's petition and the organisation has created a widget that website owners can embed on their sites, which allows their visitors to sign the petition and obtain more information about the filtering plans.

Mr Coper said GetUp's advertising blitz would begin next week, with the number of ads determined by how much money is raised. "We're thinking about putting it [the ad] on high profile news websites but also on the websites that are trafficked by the more engaged internet users - the technological websites that the regular internet users visit a lot," he said.

Despite having yet to prove the viability of its filtering plan, the Government will by the end of the year shut down the existing NetAlert scheme, which was set up by the previous government and provides free software filters to all Australian families. These are different to the filters proposed by Senator Conroy, which are mandatory and block sites from the ISP end. In 1999, Foreign Minister Stephen Smith, then the Opposition communications spokesman, told Parliament that ISP filters were "largely ineffective", citing CSIRO research that found software filters were better because they were voluntary and the level of blocking could be customised by users.

Newer tests released by the Australian Communications and Media Authority in June found available ISP filters frequently let through content that should be blocked, incorrectly blocked harmless content and slowed down network speeds by up to 87 per cent. Moreover, none of the filters will be capable of filtering non-web applications such as peer-to-peer file sharing programs. And the filters can easily be evaded by those set on accessing child pornography, using freely available tools.

During Senate question time this week, Senator Conroy refused to say how many customers an ISP would need to enlist for a trial to be credible or whether the results would be independently examined and verified. He justified the closure of NetAlert by saying it was a "monumental failure of a policy" because the free voluntary filters had attracted "extraordinarily small usage". Anti-filtering advocates have seized on those comments as a sign that there is little demand for internet filters in the first place.