Earlier this year ISIS released its 2015 budget estimated to be more than $2 billion.

While the estimate may be inflated, there is no arguing that the terrorist organization has deep pockets. In the past few years ISIS has brought in hundreds of millions of dollars through private donations,  ransom payments, extortion, robbery, antiquities trafficking, and oil sales.

ISIS has developed extensive banking networks to transfer money in and out of its controlled areas. While there have been efforts to block the transfer of funds, backdoor transfers and informal banking schemes have made it near impossible to stop.

Guest:

Greg Miller, National Security Correspondent for the Washington Post, based in D.C.; he co-wrote "Inside the surreal world of the Islamic State’s propaganda machine"