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 Abbott government. The public advice that 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. "However, a larger, more co-ordinated attack cannot be ruled out." Mr Lewis said he was comfortable that security agencies were across terror threats, but there were no guarantees an attack could be prevented.Also yesterday, federal parliament delayed a vote on new laws to strip dual-citizen jihadists of their Australian citizenship until next week, after Labor asked for more time to consider them.