Indonesia’s foremost Islamic State (IS) ideologue Aman Abdurrahman has spent more than 15 years in jail but no prison wall can seem to stop the spread of his teachings and influence to the outside world.

Following the Jakarta bomb attack last year – for which Aman has been implicated – he and four other prominent convicted militants were isolated from the rest of the facility’s population.

Counter-terrorism expert Associate Professor Kumar Ramakrishna, who heads policy at the S. Rajaratnam School of International Studies (RSIS), said: “Isolating such leaders helps stop the violent extremist ideological “virus” from spreading further amongst the prison population.”

RSIS’s Ramakrishna believes rehabilitation of prisoners needs to be put on a more systematic footing.

“The prison system is a factor but not the only one. Rehabilitation of terrorist prisoners needs to be put on a more systematic footing and better coordinated between relevant agencies. There have been some efforts in this direction though,” he said.

“Anti-terror laws that make it an offence to join IS, as well as stronger laws to criminalise violent extremist speech, are also important.”

He said that steps to improve the prospects of prison service staff and stronger penalties against low-level corruption that facilitates the ability of terrorist ideologues to communicate with the outside world are also needed.