Speaking during a rare interview in Canberra, Mr Irvine said "when you put cyber on top of [terrorism], it takes a bit of time off your sleep at night. The two issues have grown exponentially within a couple of decades and while the nature of the threats is the same, the vector has changed. And cyber is a new and very potent vector."

Mr Irvine, who led Australia's overseas spy agency ASIS before he headed up ASIO, said he'd been "horrified" at the revelations of Edward Snowden, the subcontractor to the National Security Agency who exposed vast top secret US government programs for monitoring global communications.

"People say, well nobody lost their lives as a result of Snowden, but how do you know that? You run through your mind all the possible consequences of having your capabilities, which are there to defend the country, exposed, and once exposed they become much weaker capabilities. And that was the impact of Snowden."

Mr Irvine expressed surprise at the "baldness" of the hacking of the Democratic National Committee data base (allegedly by Russia) in the current US presidential election campaign, aimed at damaging Hillary Clinton.

"There has always been in the espionage/sabotage business the use of purloined information to obtain a political objective" he said. "But the baldness of [this] is a little bit surprising, the unsubtlety even more surprising.

"The tragedy is that it restricts the freedom of our politics in a whole variety of ways, it puts strictures on our political decision makers ... they have less free conversations, become more afraid to express themselves in emails. I certainly am much more careful in the way I express myself in emails than I might have been a few years ago."

Mr Irvine was a guest at a series of security briefings for government agencies organised in Canberra this week by Australian cyber security firm Nuix. Also attending the briefings was the company's US-based vice-president, Keith Lowry, who worked at the Pentagon at the time of the Snowden leaks and lead a team trying to assess the damage from the revelations. He told Fairfax Media that many Australian government departments were "still exposed to serious data security risks because they do not conduct ongoing insider threat assessments".

Mr Irvine said cyber security was the area where those charged with protecting critical infrastructure in Australia "really had to focus in the next few years".

"You immediately think of cyber sabotage being the first tool of warfare in the 21st century but the tools that are available to nation states are increasingly available to non-state actors."

He said he wanted to see a "much stronger national cyber industry" and that while the government's recent and "probably overdue" paper on cyber security was very welcome, "the challenge now is to implement it".