Weaving political theories and his deep knowledge of history, the Home Affairs secretary Michael Pezzullo addressed an audience of other high-level bureaucrats and university students at the Australian National University's National Security College.

Mr Pezzullo provided a theoretical overview of how a nation should define national security and how government departments should work together to achieve a unified front, referencing political theorists Thomas Hobbes and the controversial Carl Schmitt.

At the core of address was a simple message: a need for all governments, the private sector and the citizenry to share the load of security in the face of growing risks.

"Security is a shared responsibility, which should be designed into our plural institutions and processes," Mr Pezzullo said, concluding his half-an-hour address.

"In order to ensure the resilience of the prosperity and unity of our nation and its character as a free and open democratic polity, we have to think of it as continuously generated effects to this end."

Last year, Mr Pezzullo outlined the country's chief risks, which he termed the "seven gathering storms". Those included the threat of a war between great powers, nuclear destruction, electoral and foreign interference and cyberattacks.

With 2020 throwing a number of curve balls, chief among them the COVID-19 pandemic, Mr Pezzullo added almost 20 more national security risks to his register, expanding beyond the typical risks associated with his field.

Climate change, the rise of fascist extremist groups, misinformation campaigns, politically-motivated groups inspired by conspiracies, the dark web all joined Mr Pezzullo's list.

General threats to humanity, such as the creation of a deadly synthetic virus, a Terminator AI threat, super volcanic eruptions and killer asteroids also needed to be considered.

"Complacency is certainly not warranted in the face of this register - please don't get me wrong - but nor is existentially pessimistic fatalism," Mr Pezzullo said.

"An exaggerated sense of ...danger ... is positively harmful as is the over application of threats. Overarming the state is as great a danger as underpowering it.

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While he backed the idea of more precise explanations behind the reasons certain documents were classified, he criticised the media for portraying the security agencies in his department as 'tyrannical', 'despotic' and 'plotting behind closed doors to oppress the Australian population'.

"It's frankly just an exaggeration, a caricature and a trope," Mr Pezzullo said.

"A Royal Commissioner could roll into my organisation and [look at] anything we're doing, at any time, and [take] out whatever they want."

While full transparency wasn't always an option, Mr Pezzullo said more information is being publicly disclosed than in previous decades and it was for the better.

"Security should be contested by informed citizenry, who share a common horizon of threat awareness, and agency in relation to risk and opportunity," Mr Pezzullo said.

"The proportionate expansion of the public discourse in this field, I think, is a very, very healthy thing."