ISIS doesn't have to look far to find customers for its multi-million dollar oil business, NBC News reported.
The group has sold $500 million in oil, according to Reuters.
In a detailed public explanation of ISIS' oil trade, Treasury Department official Adam Szubin said militants were selling as much as $40 million a month of oil at production centers then spirited on trucks across the battlelines of the Syrian civil war and sometimes further.
"[ISIS] is selling a great deal of oil to the Assad regime," Szubin, acting under secretary for Terrorism and Financial Intelligence with the Treasury, told an audience at Chatham House in London.