A leading international counter-terrorism expert from Israel has issued a warning to Australia about the success rate of deradicalisation programs.

Professor Boaz Ganor, from the International Policy Institute for Counter Terrorism, has told a meeting in Sydney only a minority of deradicalisation cases work.

"I don't believe in deradicalisation in general terms because once those people have been radicalised, it is practically impossible to uproot those ideas in their heads," he said.

"However, I'm a great believer in prevention. A lot can be done in the education and religious systems to prevent those people who might be intrigued."

Professor Ganor was speaking at a forum organised by the New South Wales Parliamentary Friends of Israel and the NSW Jewish Board of Deputies.

NSW Opposition frontbencher and deputy chairman of the parliamentary group Walt Secord said it was the difficult job of legislators to understand what programs work.

"I don't know what the answer is," he said.

"What do we do as legislators? Do we strip citizenship for foreign nationals if they fight for listed terrorist groups?

"Which programs work? It's an issue jurisdictions around the world are grappling with."

Professor Ganor said prevention was the key.

"We need to understand how terrorist groups such as Islamic State are recruiting young men and women," he said.

He said violent computer games might be fuelling some young people's desire for a so-called 'adrenaline' rush.

"Being offered by representatives of ISIS to do those barbaric things in real life — the adrenaline works.," Professor Ganor said.

Mr Secord said as legislators, one of the most important challenges is weighing up the advice of police, intelligence services and academic experts to deal with the issue of terrorism.

"Australia is touched by Islamic extremism and terrorism — in this sense we are not an island," he said.