Foreign Minister Julie Bishop says that about 150 Australians are fighting in Syria:
In Syria, it seems that over a period of time they have moved from supporting more moderate opposition groups to the more extreme, and that includes this brutal extremist group ISIS
Radicalized fighters could pose a domestic threat:
We are concerned that Australians are working with them [ISIS], becoming radicalized, learning the terrorist trade, and if they come back to Australia, of course it poses a security threat. I’ve canceled a number of passports on the advice of intelligence agencies.