There is technological sophistication behind ISIS's cash flow. Though the organization made headlines for robbing a bank in Mosul of hundreds of millions of dollars, they were doing just fine before that. It is a common misconception that terror is funded solely by donations of rich extremists. ISIS operates more like a giant organized crime syndicate and has various sources of income. Just like the mob or a gang, ISIS operatives must kick up 20% of their take from kidnapping, extortion, and other unsavory activities. The organization has also seized oil fields; they build their revenue by producing crude oil and selling electricity to Syria. They even extract and sell artifacts from areas they attack.
Just like with their social media efforts, ISIS has a sophisticated way of keeping track of their finances. They recently released a report quite similar to a financial report a corporation might release. In the report, ISIS goes over their various revenue streams, how they target their terror acts, and what sort of growth they expect going forward. They even outline their mission statement: to create a Sunni state covering portions of Iraq and Syria. Now let's take a look at how they spend that cash.