LONE wolves or small groups using basic weapons and explosives remain the biggest threats to Australia's national security. 
That advice led to Australia's new terror alert level being listed as "probable" when the alert system was launched" yesterday.
ASIO boss Duncan Lewis said "probable" was directly equivalent to the previous rating of "high", under the old system, and there had been no change to the alert level.
The old system had four threat levels - low, medium, high and extreme. The new system has five tiers which are; not expected, possible, probable, expected and certain.
It was launched this week after being approved under the former Abbott government.
The public advice which dictates the alert level continues to suggest a lone wolf attack is more likely than a sophisticated attack similar to the Paris tragedy.
"The most likely form for a terrorist attack in Australia would be an attack by an individual or a small group of like-minded individuals," the advice said.
"It is highly likely that a terrorist attack in Australia would use weapons and tactics that are low-cost and relatively simple, including basic weapons, explosives and/or firearms." Mr Lewis said he was comfortable agencies were across terror threats, but there were no guarantees an attack could be avoided.
"We have no evidence to suggest a Paris-type attack is imminent here at all," he said.
"But we have seen tragically three now lone-actor events in this country."Federal Justice Minister Michael Keenan said the new system would give agencies the opportunity to better explain the terror level.