It's the nightmare terror scenario: an extremist group building its own atomic bomb and detonating it without warning in Sydney or New York.
A new study by the Australian Strategic Policy Institute (ASPI) says it's tempting to think that the risks of nuclear terrorism are overblown.
"They aren't," ASPI says.
"If terrorists were able to overcome the still relatively significant challenges involved in the fabrication and successful detonation of an improvised nuclear device, the consequences could be catastrophic."
Authors Dr Tanya Ogilvie-White and Dr David Santoro said there were three pathways to nuclear terrorism.
Terrorists could acquire a ready-made bomb from military stocks; acquire materials to make their own improvised bomb; or they could attack or sabotage an existing nuclear facility or transportation to release radioactive material.
The paper says there's low-risk of such attack in Australia, although in 2005 police arrested a group of Islamic extremists who planned to attack the Lucas Heights reactor. But an attack anywhere in the world would still have consequences for Australia.
ASPI said Australia had internationally well-regarded technical and diplomatic expertise in non-proliferation.
Yet the former Labor government had cancelled the flagship Regional Security of Radiological Sources Project, launched in 2004.
Under that program, international experts worked under Australian leadership with regulatory bodies across South-East Asia to secure dangerous radioactive sources used in the health and industrial sectors. They also worked to develop plans to respond to nuclear attacks or sabotage.
ASPI said the government should now launch a new nuclear security strategy, including relaunching the Regional Security of Radiological Sources Project.
At a modest cost of around $2 million a year this would reduce the danger of nuclear terrorism and give Australia an international leadership role.