deena kezofsky takes a look. >> reporter: sliding oil prices hit some countries' economies more thanthers. but when it comes to terrorist organizations like others, that raises some of its revenue from selling oil at half the price on the black market, the answer as to whether or not that dip will hurt its funding may surprise some. >> oil prices are not going to have a significant impact on isis. isis relies upon a variety of income sources. they rob banks. they extort businesses. they shake down people for protection money. they break into businesses and homes and steal property. any of these outlawed terrorist-type activities are their sources of revenue. >> reporter: though oil is just one part of isis's revenue, it's not insignificant. let's look at the numbers here. officials say isis has been bringing in about $40 million per month from selling oil with about 30,000 barrels per day coming from syria and about 10,000 to 20,000 from iraq. let's not forget, though, the price of oil now is about half of what it was last summer, meaning isis is probably also making less because of