Any terrorist attack in Australia over the next year would probably involve cheap and simple weapons such as knives and vehicles, the national security agency believes.
The assessment has been put forward in the Australian Security Intelligence Organisation's latest annual report.
"Any terrorist attack over the next 12 months would probably involve weapons and tactics that are low-cost and relatively simple," ASIO's outlook for the national security environment reads.
"Globally, terrorists have used basic weapons such as knifes or vehicles to conduct lethal attacks, though explosives remain a favoured terrorist weapon."
Australia's terrorist threat level was raised to probable in September 2014 and remains there.
That means credible intelligence suggests there is an intention and capability to conduct a terrorist attack in Australia.
ASIO has disrupted 14 imminent attacks since the threat level was raised, while six attacks have been successfully carried out.
The primary terrorist threat in Australia comes from a small group of Islamic extremists, ASIO said, with the most likely form of terrorism remaining an attack by an individual or small group.
Such actors would be likely to be using simple methods but ASIO said "the possibility of more complex attacks cannot be ruled out".
The organisation's annual report also notes the trend in terrorist attacks in the West in 2017 towards targeting people at crowded places such as bridges, stadiums, public transport facilities and restaurants.
But in good news, it says there has been an overall decline in the level of propaganda produced by extremist groups such as the Islamic State.
