Local jihadists returning from the conflict in Syria pose an unparalleled security risk to Australia, experts say.
'We've never been in a situation like this before,' says Professor Greg Barton, security analyst at Monash University.
'One of the things that we're hearing from security officials in Australia and also abroad is the open acknowledgement that there is so much here that we just don't know... the fact that people are speaking so openly and so frequently about their concern and the fact that they don't know means that we're in a security situation that we haven't been in before. It's probably one of the most serious situations we've faced.'
Mr Barton believes Australia now faces a heightened risk of terrorism due to the exposure of Australian nationals in the Syrian conflict.
'We have to assume that we're more at risk than we have been in the past, we've never had a situation where so many Australians have gone off to fight in a foreign fight of this kind, particularly one that uses a narrative of Jihad.'
He said that authorities could have to deal with Australians who are so radicalised they carry on with violence when they return from the conflict.
'The challenge for us becomes if there are significant numbers coming back as to how we handle them in such a way that they don't go underground and perhaps become more of a danger to themselves and others.'
Many of the Australians in Syria are dual nationals, and Attorney-General George Brandis has flagged the possibility of stripping Australian jihadists of their citizenship.
Information about the activities of Australian nationals in Syria is limited. Of the estimated 120 citizens in the country, roughly half have joined the Al-Qaeda affiliated group Jabhat al-Nusra, which emerged in 2012 as one of the two major jihadist groups who have turned the Syrian conflict into a three-way battle.
Shandon Harris-Hogan from the Global Terrorism Research Centre says known Australians in Syria had likely engaged with local Jihad networks prior to leaving the country.
'A lot of these individuals seem to have known each other before they left or at least have individuals in common who they may have gone to the gym with or known socially,' he says. 'So through mediums like Facebook or Twitter they may have been able to communicate and actually make the path to get into Syria— whether it be via Turkey or via Lebanon— easier for other Australians who want to come and join them.'
He says that while Syria's militant groups are highly 'dangerous' and 'experienced' in conflict, many Australians who go to join them are not.
'I think there is certainly an element of naivety [amongst Australian nationals travelling to Syria]. To our knowledge pretty much none of these individuals have any type of fighting or combat experience.'
The apparent naivety of Australian fighters contrasts starkly with the character of the organisations they go to join, such as the ruthless, battle hardened groups Jabhat al-Nusra and the Islamic State in Iraq and Levant (ISIL).
This week Al-Qaeda's central leadership officially cut ties with ISIS because the group was too extreme.
Professor Barton says that both jihadist groups are hardline.
'ISIL has not just been involved in brutal fighting but imposing a very peculiar, strict understanding of Islamic law in regions that it has controlled.'
He says Australians caught up with the ISIL are cause for 'deep concern'.
'These guys are hardcore, experienced fighters... really dangerous.'
'They're very experienced and probably proportionally much more dangerous than Al-Nusra, so if Australians have ended up associating with those people then that's a deep concern.'
He also says that Al-Nusra's Al-Qaeda affiliations could persuade returning Australian citizens to carry out attacks when they get home.
'Al-Qaeda has this greater vision of going beyond regional conflict to global conflict,' he says.
According to Barton, the Australians fighting in Syria are mostly young men from Sydney's western suburbs, with some from Melbourne and Brisbane.
'The largest group of Australians come from a Lebanese background,' he says. Very few Syrian Australians have gone to Syria. The second largest group is Turkish Australians, and that's a worrying development because Turkish Australians haven't been previously involved in extremist violence.'
He believes that the bulk of the flow may have already been stopped through discouragement programs initiated by Australian authorities.
'Authorities have been working very hard through community groups to try and dissuade and discourage people from joining up... [but] critics might say we're closing the stable door after the horse has bolted.'
.