The website of the Communications Department, which is pushing a compulsory Internet filter aimed at pornography and offensive content, along with the Australian Parliament website was paralyzed for an hour due to the cyber attack, said the attorney-general's Department.
The internet filter is being promised by the country's centre-left government ahead of elections scheduled to take place later in 2010.
"No government should have the right to refuse its citizens access to information solely because they perceive it to be 'unwanted'," the hackers said in an email.
The attackers have been identified as members of anti-Church of Scientology group called 'Anonymous'.
"The Australian government will learn that one does not mess with our porn," the e-mail added.
Laws to support the filter, which would block a list of banned websites, including child abuse material and pornography, is expected to be introduced in the parliament soon.