While the prospect of radicalized Australians traveling overseas is worrisome, there is a more local, pressing problem.
There have been five terror attacks in Australia since September 2014, when the national terrorism threat level was raised, and 13 "major (counterterrorism) disruptions" -- foiled plots -- according to an Australian Security Intelligence Organization (ASIO) spokesperson.
Federal police allege they were involved in a shocking plot, the "most sophisticated" ever conceived on Australian soil, which centered around an attempt to bomb a passenger plane, though the plan was aborted.
They were also allegedly planning to launch a poison gas attack in a crowded public place.
If the perpetrators hadn't been thwarted, the attacks would have been "catastrophic," Australian Federal Police Deputy Commissioner Michael Phelan said.
The men had been in direct contact with a senior ISIS commander who sent bomb components to them in the Sydney suburbs, police allege.
With ISIS suffering defeats in Iraq and Syria, there's concern it will pull out all stops to demonstrate it remains a potent force.
Those at home -- with connections abroad -- are the ones experts say need to be watched, says Barton.
"In some cases we've got ticking time bombs. People who are broken, confused and if approached and groomed by those who want to use them, could once again become dangerous."
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There are around 600,000 Muslims in Australia, the vast majority of whom disavow ISIS' brutality.
One high-profile Muslim community leader told CNN that news that the plot was disrupted was met with relief.
"Relief because they were caught before the act, and relief for those innocent people," said Jamal Rifi, a Australian Lebanese Muslim GP, who has run his own surgery in Sydney for 27 years.
Relief too, he noted, "because just imagine the sort of backlash that would happen to the Muslim community if something like this takes place."
Many Muslim groups, particularly conservative Salafi communities in Sydney and Melbourne, say they feel under siege by the rise of conservative politics in Australia, says Clarke Jones, a criminologist at Australian National University who works in de-radicalization and counter-terrorism.
"You have people who feel racism, particularly young people who don't have those critical thinking skills. It's a complex issue, so the solutions are very complex too."
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The university student who saw two of his friends travel to ISIS-held territory says the government isn't doing enough to deter them.
"It will be a lot more worse than it is now because we are not doing enough to stop it and if (ISIS) have any means to contact people they will do it. They have nothing to lose. We do."
The government has poured tens of millions of dollars into de-radicalization programs across the country that work with communities and families to identify early warning signs.
And while prevention is hard to measure, organizers are confident they're seeing results, particularly from efforts to work with Muslim communities and their leaders to nip radicalization in the bud.
"There aren't many mothers who are going to dial a hotline and dob in a son even if they feel something is wrong," says Dellal.
"But they may do something at the grassroots level, if they're connected to people they can trust and confide in."