Islamic terrorists cannot operate without supplies. They need weapons, ammo, vehicles, communications, and all manner of other supplies to operate and survive. While terrorist groups will accept contributions of goods, they prefer cash. Thus the most successful terrorist groups are the ones who can get their hands on the most cash. For a long time one of the easiest ways to obtain a lot of cash was to kidnap a Westerner (or anyone from a wealthy family) and hold them for ransom. This only works if the potential victims make themselves available to grab. In countries where law and order are weak, those worth kidnapping tend to take good care of their personal security. Western tourists or workers in Moslem countries used to be good targets, but all it took was a few kidnappings to halt the tourism and put tight security on Westerners who had to be there. Finally, many Western countries enacted “no ransom” policies. While not always enforced, this made it more difficult, sometimes impossible, to get a lot of money for Western hostages.
There were all manner of other criminal acts terrorists could, and still do, use to obtain cash. But these all entail the risk of getting killed or captured and the locals come to consider the Islamic radicals just another bunch of bandits, and this hurts recruiting and grassroots support. When desperate, Islamic terrorists will take from whoever they can find in order to survive. But if this means angering the people they depend on for new recruits and popular support, going the bandit route is usually a sign that the group is on its last legs.
The most reliable source of funds is Islamic charities and foreign charities in general. The charity route sometimes involves deception, but often the donors know exactly where their money is going and approve of how it is used. Much of the charitable contributions come from private donations, NGOs, madrasas (Islamic religious schools), and businesses throughout South Asia, the Middle East, and Europe. Most of it tends to come from Saudi Arabia and Kuwait, where many terrorist groups have considerable support not only among local and expatriate Moslems but also patronage of the royal families and other higher ups in both these countries. This allows some terror groups to solicit quite openly. Often in the country where the terrorists are operating they can raise cash from local businessmen, industry leaders, farmers, and others willing to donate freely. These donations are collected throughout the year, sometimes in the name of religion and often, openly, for jihad.
Fund raisers will often issue receipts for donations. To placate Western nations trying to shut down Islamic terrorists the fundraisers often operate through front companies or Islamic charities and are registered as such with the local government. Donations are particularly heavy during the Hajj (the last month of the Moslem calendar when pilgrimages to Mecca are undertaken) and Ramadan (the 9th month of the Moslem calendar, when observant Moslems fast and pray a lot). The Islamic calendar is lunar, meaning it follows the phases of the moon and thus these dates move relative to the fixed calendar used in most of the world. People are much more likely to give during these two months.
Over the last decade Saudi Arabia and other Gulf Arab states have been under increasing Western pressure to crack down on this terrorist fundraising. Saudi Arabia, in particular, has cracked down since 2003 (when al Qaeda began making attacks there), after denying that there was a big problem with wealthy, and generous, Islamic conservatives in the kingdom. In the United States several Islamic charities have been successfully prosecuted since September 11, 2001, for sending money to terrorists.
Terrorist organization prefer to set up support organizations in Europe and North America, as they can safely stash their families and key operatives there by having them all claim asylum. This, until recently, was something these nations were often quick to offer and were quite tolerant of terrorist activity. But these nations, especially the ones that were subjected to terrorist attacks since 2001, are much less accommodating these days.
The terrorists constantly adapt. Decades of efforts to curb their fund raising have had an impact. It is much harder for terrorists to raise cash now, but they still do so. This has increased the importance of terrorists who specialize in fundraising. These men (and some women) develop lists of known donors, or potential ones, and assign other specialists to travel around and personally visit these donors. By way of introduction these visitors are authenticated by smartphone videos from some prominent cleric or terrorist leader, often in the presence of the visitor, saying that this man is authorized to collect funds for the cause. If a donation is forthcoming this brings into play another specialist who knows how to get the money safely from the donor to the terrorists. Meanwhile, yet another new fundraising specialist has come into play: the media advisor. Terrorists have learned that working the media (Western and in Moslem countries) is crucial for getting attention for specific terrorist groups in need of money. The media advisor recommends what types of attacks to make and what kind of press releases to put out afterward in order to get favorable attention from specific donors or groups of donors. The media advisors keep track of attitudes in countries or expatriate populations that are likely donors to identify individuals or organizations the fund raisers can approach and what types of terrorist actions will make such visits the most lucrative.
Every terrorist organization has specific needs and donor communities most likely to give. Terrorist groups that survive and thrive are the ones that are most successful at raising cash. Western counter-terror operations now concentrate on all these fundraising specialists. These fellows are wanted alive, because of all the valuable things they know. But failing that, a Hellfire missile in their SUV will work too.