The rallies, organised by members from activist groups including the Electronic Freedom Project and Digital Liberty Coalition (DLC), saw hundreds gather at Sydney's Town Hall, Brisbane Square, Melbourne's State Library, Adelaide Parliament House, Perth's Stirling Gardens and at Tasmania's Parliament Lawns to voice their opposition to the scheme.

Greens MP Scott Ludlam spoke at the Perth protests to a crowd of hundreds and questioned the need for national Internet content filtering scheme. Other speakers included members of Amnesty International, academics from state and national universities, the Electronic Frontiers Australia, and the Australia Sex Party.

Digital Liberty Coalition Brisbane rally coordinator Jasmine Marosvary said more than 15,000 people were expected to attend the rallies, which were organised through community and blog sites, Facebook and YouTube.

"The problem is not with the concept of protecting children, in fact senator Conroy has been adamant at dismissing all criticisms of his filter by alluding that the critic clearly has a stash of child porn hidden away," Marosvary said.

"It is mandatory, restricts adults to material only suitable for MA15 audiences, and filters out political communication of whatever is deemed 'hate' literature by the government in power at the time."