There can be no collective action without organization; no organization without direction; no direction without control; and no control without proper financing.

Despite all the ideological, political and social discourse surrounding the rise of extremist groups and terrorism, there is another question that must be asked regarding where they are getting the money to finance their criminal activities across Iraq and Syria. This is not to mention the terrorist groups present in Yemen and the hardline extremist organizations that have a presence across North and sub-Saharan Africa.

The sources of finance for the Islamic State of Iraq and Syria (ISIS), for example, are well known, and the same goes for other terrorist organizations of its ilk. ISIS gets a large portion of its fund from sympathizers outside of Syria and Iraq, including through criminal organizations that put themselves forward as charities and NGOs. Then there is the ransoms paid to secure the release of foreign hostages. Following the execution of US journalist James Foley, it was revealed that ISIS had demanded 132 million US dollars to release him, so the kinds of figures that the group is paid in ransom is clear to see.

ISIS has also endeavored to control oil and gas production in areas under its control in Iraq and Syria, as well as factories and even accommodation services. ISIS is selling oil and gas on the black market, through Turkish and Kurdish intermediaries; this is perhaps the terrorist group’s biggest source of revenue. However ISIS is also selling oil products locally, with some reports estimating that it is able to secure revenue around 1.5 million US dollars per day from this.

The terrorist group has also outright stolen massive amounts of cash from banks in territory under their control, including the central Bank of Mosul. Estimates indicate that they could have obtained as much as 425 million US dollars from this brazen policy.

This is not to mention ISIS’s trades in weapons and military equipment; the group managed to get its hands on sophisticated arms and expensive military vehicles that were left behind by retreating Iraqi military units.

Some of these sources of funding are beyond our ability to deal with, however we can address some issues. We must particularly be alert to the donations that ISIS receives from foreign sympathizers. In an infamous TV clip that has since gone viral, Kuwaiti Preacher Hajjaj Al-Ajami openly bragged that foreign governments are incapable of uncovering and stopping funding from being delivered to the Al-Nusra Front and similar groups in Syria.

There are billions of dollars—and this is not an exaggeration—being moved around around the world to fund terrorism and unfortunately this includes money from people who—either out of ignorance or a misplaced desire to do good—are supporting these criminal groups.

We must trace this funding, wherever it comes from and wherever it leads. If we are able to turn off the tap of this funding, terrorism and extremism will suffocate.