According to some leaks from the ISIL sites and news, stealing and abduction are mostly the sources of finance the ISIL uses according to the “Times” magazine
To conquer you need weapons. And you need money to get weapons as you all know.
And according to the magazine, the state of AL Mosul was their biggest financier . 10178790 American $ monthly to get weapons and equipment. And other sources of money was from the Syrian and Iraqi Oil they had been selling for 50+ million dollar according to the Iraqi National Congress leader Ahmed Chalabi .
He adds: ISIL finances itself through its control over some oil pipelines.
In April / May last Iraqi authorities announced the arrest of Mohamed Mahmoud Omar al-Dulaimi,one of the financiers of “ISIL” and declared that he have been distributing more than four million dollars a month between the states in Iraq that are under the control of the ISIL.
Finally the Al Safir announced that the ISIL have , need more supplies of weapons before Ramadan, so they prepared a bigger scheme …a scheme that imposes more looting and murder to secure more money / before the next Ramadan
