Extremists' posts are recruiting the vulnerable: spy boss

Social media is enabling extremists to air their bloody doctrine like never before, easily radicalising young followers at home, according to Australia's top spy.

During a speech last night, ASIO chief David Irvine attributed the rise of new technologies such as Twitter and Facebook to a growing number of Jihadist supporters abroad, saying those most isolated in the community made easy picking for radical groups, the Sydney Morning Herald reports.

"Extremists use this new media to disseminate their message, interactively bringing their gory barbarity back to Australia, with the aim of radicalising young Australians in real time as they sit at home or wait for buses and trains in the morning," he told the Institute of International Affairs.

Mr Irvine said Australian jihadists such as Sydney's Mohamed Elomar and Khaled Sharrouf, who recently posted an image of his seven-year-old son holding the severed head of a soldier in Syria, were revelling in their newfound notoriety.

Their gruesome posts served to recruit other English-speaking Islamists, as well as spreading panic and fear, he said.

"And it has been Australians who have been doing this, Australians involved with the worst of the worst in terms of extremist groups inside Syria and Iraq," he said.

Mr Irvine, who used the speech to defend proposed legislation to surveil Australians, stressed that extremists represented only a small minority of the Muslim community, praising Islamic leaders' "outstanding" efforts to curb radicalism.

But he said that, much like Afghanistan in the 1990s, the conflicts in Syria and Iraq could create a new wave of Islamic extremism felt for years to come.

"We can't afford to get that balance wrong," he said.