Australian Signals Directorate director general Rachel Noble said a quarter of all cyber attacks the organisation responded to were levelled against critical infrastructure like energy, water, telcos and health services.

Malicious state actors would attack these systems to try and gather intelligence or implant bugs and malware that would be able to deny, degrade or disrupt these services whenever they choose.

But the strength of Australia's cyber warfare capabilities means adversaries should think twice about the benefits of launching an attack, Ms Noble said.

"We never seek conflict," she said on Thursday.

"ASD is increasingly becoming the first and last line of digital defence that protects our country from cyber attacks ... and we are right now fighting that battle with criminals, state actors and serious and organised crime.

"But we do want our adversaries to know that we are here. We want them to calculate: Today is not the day."

Ms Noble said Australia's intelligence capabilities allowed the directorate to "undertake offensive cyber operations like no one else can".

Offensive operations have also grown to the stage that they would be able to shorten any war Australia gets involved in, she said.

The speech came a day after Prime Minister Scott Morrison spruiked that Australia's new trilateral security partnership with the United States and Britain would enhance cyber capabilities, artificial intelligence, quantum technologies and undersea capabilities.

"AUKUS is a broad and adaptable partnership that will drive our technology and capability cooperation to meet the challenges of the 21st century in the Indo-Pacific region," he said.

Australian Associated Press