Indonesian hackers have crashed the website of Australian intelligence agency ASIS, according to hackers and cyber experts, dramatically stepping up the revenge attacks in response to the spying affair.

On Monday afternoon the website of the Australian Secret Intelligence Service was still not working.

The hacked ASIS website.

Heru Sutadi, executive director of Indonesian technology think tank the Indonesia ICT Institute, confirmed that hackers from the country had launched a successful "distributed denial of service" attack, which crashed the website.