Hackers disabled several Australian government websites.
Computer hackers have attacked official websites in Australia in a protest against a proposed internet filter to target pornography and criminal sites.
The Australian parliament's website was disabled for almost an hour by a group calling itself Anonymous.
A statement attributed to the group said the Australian government should not try to control what people viewed on the internet.
The government plans to introduce a mandatory filter by early 2011.
This latest attack mirrors a similar one in November last year which was also carried out by the group.
The government communications department told the Reuters news agency that in this latest attack, the hackers had not infiltrated government security, but had instead swamped government computer servers.
The Australian government, which faces elections this year, has promised an internet filter that would block a list of banned websites, including those containing child abuse material.
Alastair MacGibbon, a former director of the government's High-Tech Crime Centre, told the Australian Broadcasting Corporation that internet hackers were difficult to combat, because the technology would shut down "a whole range of other legitimate commerce and legitimate government business".
But he said that compared to most Western nations, Australia was "well prepared" for such attacks.