To plan and conduct their attack, the 9/11 plotters spent somewhere between $400,000 and $500,000, the vast majority of which was provided by al Qaeda. Although the origin of the funds remains unknown, extensive investigation has revealed quite a bit about the financial transactions that supported the 9/11 plot. The hijackers and their financial facilitators used the anonymity provided by the huge international and domestic financial system to move and store their money through a series of unremarkable transactions. The existing mechanisms to prevent abuse of the financial system did not fail. They were never designed to detect or disrupt.
