ISIS has over $2 billion in the bank, more than some small countries such as Tonga and the Marshall Islands, according to information captured on a batch of 160 flash disks. The majority of the wealth comes from seizure of assets by the group in its takeover of Mosul. A senior intelligence official:
By the end of the week, we soon realised that we had to do some accounting for them. Before Mosul, their total cash and assets were $875 million. Afterwards, with the money they robbed from banks and the value of the military supplies they looted, they could add another $1.5 billion to that
It also has income from oilfields in northeastern Syria captured in 2012, smuggling of raw materials, and looting of the Assad administration’s crumbling government assets, but the extra cash allows the group to operate as a de facto caliphate in its own right:
They had taken $36m from al-Nabuk alone [an area in the Qalamoun mountains west of Damascus]. The antiquities there are up to 8,000 years old. Before this, the western officials had been asking us where they had gotten some of their money from, $50,000 here, or $20,000 there. It was peanuts. Now they know and we know. They had done this all themselves. There was no state actor at all behind them, which we had long known. They don’t need one.