Terrorism is a use of violence for selfish or political purposes. The 2001 incident of 9-11 is a prime example of terrorism. Often times terrorism is performed by non-state actors and achieves their agenda through coercion and intimidation. Acts of terrorism are unlawful, destructive and illegitimate. There are a few types of terrorism, namely civil disorder, political terrorism, and official/state terrorism. Civil disorder is a form of violence that creates fear within a community and hinders peace and security. Political terrorism is violent behaviour that seeks to intimidate and threaten in order to achieve a specific political purpose. State terrorism involves nations that rule through intimidation, fear and violence. Non-state actors are agents who are not affiliated with any sovereign state and are therefore under no authority other than their own. These non-state actors act within the international sphere, but it is hard to trace them or make them accountable. This the primary issue with international security against terrorism.
International security as a concept has seen a large evolution of ideas. Traditionally, international security has revolved around protecting the state. This follows the theory that the protection of the citizens will follow as long as the state is protected. This theory found its height in the Cold War. But, since then, many different approaches have arisen including: classical realism, neorealism, economic liberalism, and liberal institutionalism. It is important to remember that military protection is not the only concern of international security. For example, economic security is just as important.