'Communications were degraded within seconds'

It is understood the ISIS commanders were communicating on encrypted messaging apps, which can't be decoded, and so ASD operatives cut off their connection to the internet.

And it was all done from the basement of Defence headquarters in the Canberra suburb of Russell.

"Just as the coalition forces were preparing to attack the terrorists’ position, our offensive cyber operators were at their keyboards in Australia – firing highly targeted bits and bytes into cyberspace," Mr Burgess will say.

"Daesh [ISIS] communications were degraded within seconds."

The description given by Mr Burgess fits with the campaign to retake the northern city of Mosul from ISIS, which lasted nine months, and involved international troops supporting the largely untested Iraqi army.

Australia disclosed its offensive cyber capability in 2016 under prime minister Malcolm Turnbull, and Mr Burgess will say it has become a critical part of the country's military arsenal and is now a vital part of supporting front-line troops.

Out of the shadows


The ASD hacking of ISIS internet connections was believed to be a unique Australian capability at the time, but the United States and others have quickly acquired similar technological skills.

Under Mr Burgess, ASD has by its own admission "come out of the shadows".

In a speech last October, he laid out the case for why the federal government had banned Chinese telecommunications equipment makers Huawei and ZTE from building Australia's new 5G mobile networks.

Mr Burgess said the electricity grid, water supplies and other critical infrastructure could not have been adequately protected if the Chinese vendors had been allowed to participate.

"This is about more than just protecting the confidentiality of our information – it is also about integrity and availability of the data and systems on which we depend," he said.

In his speech on Wednesday, Mr Burgess will also seek to dispel the myth that cyber operations are always conducted by young men wearing black, who can instantly destroy a network or blow something up.

"Many of our operations are carefully designed to achieve the objective in a much more subtle and sophisticated way," Mr Burgess will say.

"For example, our targets may find their communications don’t work at a critical moment – rather than being destroyed completely."