The so-called “nexus” between organized criminal and terrorist organizations is a topic of increasing national and international security interest. The four most resilient and debilitating sectors of organized international crime affecting state security are human, weapons, drug and contraband trafficking (HWDC-trafficking). Sometimes interconnected and mutually supporting, HWDC-trafficking is not only pervasive in states where there is a culture of corruption, but also in democratic states where traffickers take advantage of the freedoms enjoyed in liberal democracies. HWDC-trafficking is responsible for channeling multiple billions of dollars in profit to criminal and terrorist organizations worldwide. Many believe HWDC-trafficking, in its most insidious forms, has been increasingly linked to the activities of violent extremist organizations such as al Qaeda and like-minded groups. To what extent the two types of entities cooperate is not clear and a matter of much debate. Some analysts frame the interactions among terrorist and criminal organizations as symbiotic alliances in which the comparative advantages among organizations determine divisions of labor for mutual benefit and profit. Others liken the relationships to short-term “marriages of convenience” that are executed for specific transactions and events.