The website of Australia's overseas spy agency ASIS remains down after apparently being crashed by Indonesian hackers.
The distributed denial of service (DDoS) attack is believed to have been carried out by the Indonesian arm of the Anonymous hacker group on Monday, in retaliation to claims Australia uses its Jakarta embassy to spy on its northern neighbour.
A DDoS attack paralyses computer systems by overwhelming them with online requests.
The Australian Secret Intelligence Service (ASIS) website is used mainly as a recruitment tool and contains very little information about the organisation.
RMIT University internet security expert Dr Mark Gregory said there could be no doubting the attacks originated from internet groups out of Indonesia.
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It followed the attacks on more than 100 small Australian businesses, charities and government organisations by Indonesian hackers over the past week, he said.
"It highlights that Australia needs to look at how it can harden itself against this type of attack," he said.
The Department of Foreign Affairs and Trade, which oversees ASIS, said they would not be commenting on the website crash.
One group believed to be affiliated with the attacks, the Indonesian Security Down Team, sent a message out to its group via Facebook on Tuesday to prepare for for a cyber war.
"You want Cyberwarfare? I give you now. WE ARE READY FOR CYBERNETIC WAR," the message said.
The post came just hours after the group boasted with a screenshot claiming the website of the Australian Security Intelligence Organisation (ASIO), the nation's domestic spy agency, has also been brought down on Tuesday morning.
Comment has been sought from ASIO, but its site was running as of Tuesday afternoon.
