Book excerpt: It is an axiom within the U.S. law enforcement and intelligence communities that "following the money" is the key to disrupting and dismantling criminal organizations. The same is true when it comes to terrorist networks. Officials in the United States and abroad now realize that fighting terrorism financing (and its corollary, money laundering) is one of the best ways to prevent future catastrophic attacks. As a new generation of public servants learns the ropes and begins to contribute to the war on terror, the proven tactic of following money trails will become more central than ever. At the same time, this task is becoming increasingly complex due to our adversaries' skill in avoiding traditional financial countermeasures. Law enforcement and intelligence officials must learn to understand the sometimes obscure methodologies that terrorist organizations use to raise, move, and store money-whether these activities stem from the Usama bin Ladens of the world, rogue regimes like Iran and North Korea, or members of Hizbollah, Hamas, or a host of other like-minded organizations.