France bombed ISIS targets in Syria on Sunday — in retaliation for Friday's terror attacks in Paris — including a training camp and an ammunition depot, according to the French Defense Ministry. The next day, the United States targeted 116 trucks ISIS had been using to transport oil. The latter strike, reportedly planned before the Paris attacks, is an attempt to stymie a source of funding for the extremist group.
ISIS derives most of its funds from activities inside the territories it now controls, said Daveed Gartenstein-Ross, a senior fellow with the Foundation for Defense of Democracies. That’s different from, say, Al Qaeda, which has historically relied on donations from outside sources.
"When they control a territory that’s approximately the size of Great Britain, that creates a great deal of ability to get internal sources of revenue, ranging from natural resources, to antiquities they control, to taxation on their population," he said.
It’s hard to say just how much funding ISIS gets from each source. Gartenstein-Ross estimates that the largest piece of the pie comes from taxing the people in its territories.
The group also benefits from the sale of antiquities from sites it loots.
"We’re really talking about small items, so tablets or seals," said Howard Shatz, a senior economist at the Rand Corporation. "You can put those in your pocket, you can put them in a suitcase."
Shatz said middlemen can get the goods to private buyers or lower-tier auction houses.
Meanwhile, oil is often transported across long-standing smuggling routes and mixed with oil from other sources so it can’t be traced, said Matthew Levitt, director of the Stein Program on Counterterrorism & Intelligence at the Washington Institute for Near East Policy.
The group makes use of hidden compartments in trucks as well as hoses to transport oil across borders, often into southern Turkey.
Still, other funding comes from ransoms demanded for kidnap victims.
"The vast majority of this money is going to run their state, because that's their biggest expense by far," said Levitt. "But they have a lot of money. If they want to be able to peel off a little bit for terrorism, they can do a tremendous amount of damage."
While funding sources for the Paris attack are not yet clear, Levitt said similar attacks typically cost in the thousands or tens of thousands of dollars and are often funded by criminal activity near the target.