The federal government has raised Australia's National Terrorism Threat Level from "possible" to "probable".
Prime Minister Anthony Albanese announced the update after a meeting of the national security committee and cabinet this morning.
Albanese stressed that "probable" does not mean "inevitable".
Here's what it means:
What does raising the terror threat level to 'probable' mean for Australia?
The official definition of the terror threat being raised to "probable" is that there is a greater than fifty per cent chance of an onshore attack or attack planning in the next twelve months, according to National Security Australia
"The national terrorism threat level is a warning tool to provide government and the public an indication of what ASIO is seeing and anticipates in the near future," it says.
"The security environment will continue to change in response to issues and events that arise both in Australia and overseas.
"The government will continue to provide updated advice to the Australian community as these changes occur."
Attacks in Australia are likely to be low-cost, using readily available weapons, and simple tactics, it says.
They are most likely to be carried out by an individual or small group in a crowded place such as a shopping centre or transport hub.
"Basic weapons, such as knives, vehicles, explosives, and firearms can maximise casualties when combined with simple tactics," it says.
"How perpetrators identify targets to attack can be driven by the ideology, or grievance of the attacker, and may include symbolic locations such as government buildings, places of worship or specific events."
Why has the threat level been raised
Intelligence experts say the decision to raise the threat level was not triggered by any single ideology or issue, but reported an overall rise in polarisation in Australia and other Western nations.
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Albanese said he sought to reassure Australians that "probable does not mean inevitable and it does not mean it is intelligence about an imminent threat or danger."
The director-general of Australia's domestic intelligence service ASIO, Mike Burgess, said that the country's security environment is "more volatile and more unpredictable".
"More Australians are embracing a more diverse range of extreme ideologies and more Australians are willing to use violence to advance their cause," he said.
"Politically motivated violence now joins espionage and foreign interference is our principal security concerns."
Burgess also stressed that "probable does not mean inevitable", but said "radical and inflammatory views are being normalised".
"This trend increased during Covid and gained momentum after the terrorist attacks on Israel, and accelerated during Israel's military response," he said.
"Individuals are embracing anti-authority ideologies, conspiracy theories, and diverse grievances."
The National Security Australia website warns social media is a "key driver of volatility," adding it is "acting as a gateway and platform for violent ideologies and global influences to promulgate at volume and scale."
Australia's terror alert system
The National Terrorism Threat Advisory System has a scale of five levels.
They go from the highest, "certain" followed by "expected", "probable", "possible" and the lowest, "not expected".
The system informs the Australian Government's national security preparedness and response planning.
When was the last time the threat level was raised
The terror threat level has not been raised for ten years, since 2014.
It was last changed in 2022 when it was lowered to "possible".
Before that it was "probable."
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