The anthrax attacks in the United States have represented a fundamental shift in the nature of the biological terrorism threat. There have been at least three possible, but unlikely explanations for the origin of the anthrax found in a letter sent to Senator Daschle that include: (1) the attacks were the covert act of a state looking to inflict harm or a move towards wider conflict; (2) a state illicited a terrorist group to conduct the attack or provided the substance to a sub-national entity; and (3) a terrorist group or individual produced the anthrax or received assistance from scientists selling their knowledge. The quality of anthrax sent to the U.S. Senate had characteristics associated with state biological weapons programs. States have the feasibility and capabilities in using biological weapons. There were three circumstances identified when a state might engage in biological warfare: (1) when a state is struggling for its existence and wants to prevent defeat; (2) when a state feels it could attack with biological weapons and be undetected; and (3) when it attacked its own citizens. Even with the resources and capabilities to wage biological terrorism, there are considerable disincentives from doing so. Despite the recent anthrax attacks, the history of biological warfare, terrorism, and crime is seen as less deadly than the history with conventional explosives. Even though a biological terrorist attack is seen as remote, the government has the responsibility to prevent, protect, and respond to incidents that seem unlikely. Preventive nonproliferation measures are the basis for a frontline of defense against biological weapons attacks. Preventive nonproliferation measures discussed included those highlighted under the Biological Weapons Convention, the Conventional Forces in Europe, the UN General Assembly, the Australia Group, the Chemical Weapons Convention, and the Harvard Sussex Program on CBW Armament and Arms Limitation.