Terrorism is frightening because it is unpredictable. Modern terrorist groups use portable weapons, function in small decentralized cells, often receive funds from drug trafficking, emphasize flexibility in their operations, and are increasingly urban. Terrorism differs from insurgency in that it is conducted by a small group. It also differs from State terror, which occurs through the abuse of legitimate power. Wilkinson has defined four types of terrorism: criminal, psychic, war, and political. One of the aims of terrorism is to provoke the authorities into using illegal, unconstitutional, and repressive measures and thereby to lose public support.