Terrorism has been explained as a doctrine and method of struggle for certain purposes by means of systematic use of illegal force. The notions of terror and terrorism, although essentially based on the spread of fear through violence, is often differentiated as such: terror is qualified as the inducement of fear and violence in an organized and institutional way by a State apparatus against its citizens, while terrorism is applied to the method practiced by individuals and groups in order to achieve own interests. Applied to both situations, terrorism can be defined as a criminal activity accompanied by the use of illegal force and other methods of violence by individuals, groups, networks or institutions with the intent to cause mass fear, insecurity and mistrust among citizens towards their own institutions, in order to force governments to promote their political, ideological, economic and/or religious interests. Nowadays, terrorism also appears as a method in conducting hybrid war, where sponsoring and interfering States officially deny any such sponsorship and even deeply condemn those operations. The problem of “inability” to define terrorism at the international level has become a serious obstacle to its being placed under social control. An inadequate perception of democratic institutions about a problem creates inadequate social control. Lack of proper social control reflects in inadequate normative/institutional law-enforcement corpus competent for detecting, preventing and fighting crimes. The fight against “terrorism” has been paradoxically implemented, hence its poor successes. This paradoxical situation, opposing the reasons of economy to the reasons of human security, cannot be resolved without a fundamental resolution of internal, deep contradictions in the very essence of contemporary society, by means of a qualitatively new socio-economic and political system, a truly free, humane and pluralistic society.