Citing Crowbat (in part):
more than 300 Kurds were recruited for the Daesh alone in Evin Prison, in Tehran, in 2013.
I am aware that Iran has a Kurdish community, although not one noted to my knowledge for being a violent insurgency. So there are Kurds in the Iranian prison system, whether for criminal or political reasons. IIRC Evin Prison is for political prisoners, Wiki states only a 'wing' is so used:http://en.wikipedia.org/wiki/Evin_Prison

So Kurds were covertly recruited in the prison, that I can follow as few prisons have total control - though a political wing can be different (as Israel has shown). I am wary about such a prison allowing 'radical' Islamists to flourish. Those recruited presumably hate the Iranian regime and have cause to wage war upon release - making their way to Iraq / Syria to join Daesh.