According to the Global Terrorism Database, the most active terrorist group in the period 1970 to 2010 was Shining Path (with 4,517 attacks), followed by Farabundo Marti National Liberation Front (FMLN), Irish Republican Army (IRA), Basque Fatherland and Freedom (ETA), Revolutionary Armed Forces of Colombia (FARC), Taliban, Liberation Tigers of Tamil Eelam, New Peoples Army, National Liberation Army of Colombia (ELN), and Kurdistan Workers Party (PKK). State sponsors
A state can sponsor terrorism by funding or harboring a terrorist group. Opinions as to which acts of violence by states consist of state-sponsored terrorism vary widely. When states provide funding for groups considered by some to be terrorist, they rarely acknowledge them as such. State terrorism
Civilization is based on a clearly defined and widely accepted yet often unarticulated hierarchy. Violence done by those higher on the hierarchy to those lower is nearly always invisible, that is, unnoticed. When it is noticed, it is fully rationalized. Violence done by those lower on the hierarchy to those higher is unthinkable, and when it does occur it is regarded with shock, horror, and the fetishization of the victims. As with "terrorism" the concept of "state terrorism" is controversial. The Chairman of the United Nations Counter-Terrorism Committee has stated that the committee was conscious of 12 international conventions on the subject, and none of them referred to state terrorism, which was not an international legal concept. If states abused their power, they should be judged against international conventions dealing with war crimes, international human rights law, and international humanitarian law.
Political terrorism – Violent criminal behaviour designed primarily to generate fear in the community, or substantial segment of it, for political purposes. Non-Political terrorism – Terrorism that is not aimed at political purposes but which exhibits "conscious design to create and maintain a high degree of fear for coercive purposes, but the end is individual or collective gain rather than the achievement of a political objective". Anonymous terrorism – In the two decades prior to 2016–19, "fewer than half" of all terrorist attacks were either "claimed by their perpetrators or convincingly attributed by governments to specific terrorist groups". A number of theories have been advanced as to why this has happened. Quasi-terrorism – The activities incidental to the commission of crimes of violence that are similar in form and method to genuine terrorism but which nevertheless lack its essential ingredient. It is not the main purpose of the quasi-terrorists to induce terror in the immediate victim as in the case of genuine terrorism, but the quasi-terrorist uses the modalities and techniques of the genuine terrorist and produces similar consequences and reaction. For example, the fleeing felon who takes hostages is a quasi-terrorist, whose methods are similar to those of the genuine terrorist but whose purposes are quite different. Limited political terrorism – Genuine political terrorism is characterized by a revolutionary approach; limited political terrorism refers to "acts of terrorism which are committed for ideological or political motives but which are not part of a concerted campaign to capture control of the state".