The head of Australia's domestic spy agency says the terrorism threat, while high, is plateauing.
Australia's spy chief Duncan Lewis says the terrorist threat is plateauing in Australia, but the scale of hostile foreign intelligence activities is unprecedented.
The Australian Security Intelligence Organisation's director-general Duncan Lewis appeared before a Senate estimates hearing in Canberra on Monday afternoon.
The threat of a terrorist attack and foreign intelligence activities are posing the biggest threats to Australia, Mr Lewis said.
"Both of these are compounded by the rapidly changing technologies that are afoot," he said.
But, the head of Australia's domestic spy agency says the threat of foreign interference is growing stronger.
"The current scale of foreign intelligence activity against Australian interests is unprecedented," he said.
"Hostile intelligence activity poses a real and potential existential threat to Australian security and sovereignty."
While he did not single out specific countries, Mr Lewis said there was "no evidence" Russia was posing a risk to the upcoming federal election.
"The issue is more diverse than it was, say, during the period of the Cold War where the boundaries were fairly distinct," Mr Lewis said.
"It's more of a crowded space."
More Australian foreign fighters killed
The number of Australians confirmed by ASIO to have been killed fighting with IS in the Middle East.
The organisation now believes 90 to 94 Australians have been killed in Iraq and Syria, a small increase since its last appearance before parliamentarians.
"Since 2012, there have been about 230 Australians that have travelled to Syria or Iraq to fight with or support groups involved in the conflict," Mr Lewis said.
"Around half of those Australian travellers ... are still active in the conflict."
The most likely terrorist attack in Australia would come from a so-called 'lone wolf' or small group. But, a more "complex" attack could not be ruled out, the ASIO official said.
Israel advice was 'routine'
The domestic intelligence agency also played down the significance of a leaked memo which said the Morrison Government's proposal to relocate its embassy in Israel could provoke violence.
The prime minister last week said he was open to moving the embassy from Tel Aviv to Jerusalem.
Mr Lewis said there was no specific indication the controversial proposal would spark protests or violence in Australia but did not extend to other countries.
"It was a routine piece of advice," Mr Lewis told the committee.