The battle against the Islamic State group's extremism may last a generation, Australian Foreign Minister Julie Bishop has warned, likening the jihadists to fanatical followers of Adolf Hitler.

Bishop said the pernicious threat of global terrorism was one that "keeps me awake at night" and urged a strong counter-narrative to the messages of hate and division spread by violent extremists.

"It is crucial that this is not portrayed as a struggle that can be defeated militarily in far flung battlefields. This is a struggle against a malignant idea, a concept, an ideology," she said in a speech in Canberra late Tuesday.

"We have no choice but to be part of this struggle against extremism in all its forms, both home and abroad, this will take years, decades, potentially a generation -- to resolve."

Bishop said the self-named Islamic State group, also known as Daesh, used social media to obscure the truth and plant propaganda as she noted a parallel with Hitler's drive to build a new order to last a millennium.

"Daesh is attempting to emulate this approach with its declaration of a caliphate, claiming to establish a 'pure' form of government that will attract the fanatical supporters willing to die for the cause," she told the Institute of Regional Security.

Australia and other Western countries are grappling with hundreds of citizens who are leaving comfortable lives to become fighters for IS in Iraq and Syria, with at least 90 Australians known to be in the conflict zone.

Bishop said while it could be rationalised why those with long criminal histories, mental illness and drug abusers would travel to a battlefield, it was more difficult to understand why young men would want to "drag the world back to the Dark Ages".

"It is even harder to explain why young women from similar backgrounds would be motivated to join an organisation notoriously vicious in its degrading treatment of women and girls," she said.

Thanking the Australian Muslim community for their support, Bishop said the government needed to find a way to protect the vulnerable from "the siren song of the extremists luring our people to stage attacks on our soil or encouraging them to a senseless death".