There are two things, in particular, that Islamic terrorism needs to keep going; cash and publicity. These two items are what fuel and munitions are to a conventional army. Stopping terrorists from obtaining cash and publicity is is difficult. Cash has been easier to deal with. So far, the United States has frozen some $200 million in funds that were held by organizations, usually Islamic charities, that were found to be passing the money on to terrorists. Currently, Islamic terrorists are spending nearly $40 million a year to keep their operations international going. That's not a firm number, because "international Islamic terrorism," often gets mixed up with the local variety. Iraq is a prime example, where most of the violence is about local issues (Sunni Arabs trying to regain power, Shia Arabs seeking revenge against Sunni Arabs). Same thing in Afghanistan, where a lot of the "terrorism" is basically tribal politics. The "Taliban" is a coalition of Pushtun tribes with shared religious and social values (both of which are conservative in the extreme, and not accepted by many other Afghans.)
But al Qaeda recognizes that these local Islamic radicals are often willing to join forces. That's what happened in Iraq in 2004, when al Qaeda and Sunni Arab nationalists (trying to regain power), joined together. In that case, it was the Sunni Arabs who had more money, and for at least a year, provided al Qaeda with millions of dollars a month. That largess has since shrunk, because of al Qaeda's tendency to use indiscriminate suicide car bomb attacks. As a result, al Qaeda has reduced operations in Iraq and shifted more money to Afghanistan, where the Taliban are easier to manage.
Counter-terrorism organizations have been able to intercept, or at least block, a lot of the money intended for Islamic terrorists. It's been more difficult to interfere with the pro-terrorist media message. It's a sad fact that Islamic terrorism is quite popular among many Moslems. In late 2001, Al Qaeda's "approval rating" was over 50 percent in most Islamic countries. But by 2005, all those images of dead Moslems in Iraq, and elsewhere, cut this approval substantially (often to single digits.) But that number can rise again, because politicians in Islamic countries have, for decades, been blaming the "West" for all the bad things (corruption, inept government) they were presiding over. Now that sort of blame-shifting is good politics (for the politician, anyway), but it has backfired, because al Qaeda's main targets are these same Moslem politicians. Thus when al Qaeda made a big mess in the United States in 2001, many Moslem politicians were privately glad to see it. But now that the terrorists have brought their mayhem home, it's another story. However, when al Qaeda gets smart, as they have in several countries of late, and stopped their local attacks on Moslems, the population will, after a few months, begin to admire al Qaeda again. With that comes more money and recruits. And as those approval ratings rise, fewer Moslems are going to cooperate with the police.
For a number of reasons, Western media has a hard time understanding how important it is to keep the Islamic terrorists doing their dirt in Islamic countries. Every al Qaeda attack in Iraq, and the majority of them kill Moslems, hurts al Qaeda's image in the rest of the Islamic world. Attacks in the West, however, make al Qaeda appear mighty in the Islamic world. Do the math. Al Qaeda has.