Two men who claim to be from online group Anonymous have been arrested in Perth and Sydney for allegedly hacking into Australian and international websites.



The Australian Federal Police (AFP) said the men were arrested after searches of their homes in Penrith, New South Wales, and Scarborough, Western Australia.



Several computer hard drives and other equipment were seized, and it is expected to take several months to analyse the items due to the amount of information stored on them.



The AFP said it would be alleged in court that the men knew each other online and targeted organisations including a large internet service provider and web servers hosting Australian and Indonesian government websites.



The 40-year-old Scarborough man was charged with aiding the unauthorised modification of Melbourne IT Ltd's computer network in Brisbane to cause impairment and unauthorised modification of Indonesian government web servers to cause impairment.



He is scheduled to appear in Perth magistrates court on Thursday.



The 18-year-old Penrith man was charged with unauthorised modification of data to NetSpeed ISP in Canberra to cause impairment, and unauthorised access to and modification of restricted data belonging to the ACT Long Service Leave Board in Canberra.



He is due to appear in Sydney central local court on Thursday.



The AFP said people claiming to be members of Anonymous had targeted Australian government and corporate networks for the past two years.



The attacks had resulted in theft of personal data, defacement of websites and distributed denial of service attacks, causing websites to drop offline, the AFP said.



A distributed denial of service attacks is one in which a multitude of compromised systems attack a single target.



"These acts can cause serious disruption to government and business networks, which in turn can be catastrophic for people who rely on these networks to run their small business or administer their entitlements or personal finances," the AFP’s national manager of high-tech crime operations, Tim Morris, said.



"The impairment or disruption of communications to or from computer networks is a criminal act and can have serious consequences – it is not harmless fun."