As a rule, terrorist attacks can be divided into two types: “personal initiative” attacks, and “organized terrorism.”In organized terrorism, a terrorist organization is involved in one, some, or all of the stages of a terrorist attack: initiation, planning, preparation, perpetration. A terrorist organization may initiate an attack that is ultimately perpetrated by others unaffiliated with it. Or one organization may help another organization or group conduct a terrorist attack by passing on intelligence, supplying weapons, training the attackers, or providing funding.The author is the Ronald Lauder Chair for Counter Terrorism, founder and executive director of The International Policy Institute for Counter-Terrorism (ICT) and deputy dean of the Lauder School of Government at The Interdisciplinary Center Herzliya.Alternatively, an organization may initiate, plan and prepare an attack so that others can execute it. All of these scenarios constitute “indirect organized terrorism.” On the other hand, in “direct organized terrorism,” a terrorist organization may be involved in all stages of the initiation and preparation of an attack, and then in fact send its own operatives to perpetrate it.Direct organized terrorism may be implemented by one of a terrorist organization’s local cells, sleeper cells, or individual activists.In contrast, a personal initiative terrorist attack is one in which no terrorist organization has played any part. No organization initiated it, no organization planned it, no organization prepared it, and its perpetrators were not members of any terrorist organization. In some cases, a terrorist organization may inspire or incite a local terrorist network or “lone wolf” to perpetrate an attack, even without taking any active part in the specific attack.A personal initiative begins and ends in the febrile mind of an individual, or in the dark discussions of a local group which, for whatever reason, has decided to launch a terrorist attack. When a personal initiative attack is carried out by an individual who is neither affiliated with nor sent by a terrorist organization, we say he or she has acted as a “lone wolf.” His or her motives may be personal-psychological, allied with the motives of a local group, or derived from global political motives.The psychologically-driven lone wolf may be responding to an internal imperative born of a past traumatic incident (however, if this incident and the response to it are not political, then the lone wolf’s attack is a crime, and not terrorism, and constitutes murder or attempted murder). The lone wolf impelled by local imperatives may be responding to a local political situation – that is, to the statements, events, processes or decisions of his municipal, state, or even federal government (e.g., recent efforts to increase gun control in the United States).The lone wolf inspired by global political considerations usually decides to carry out a terrorist attack after protracted exposure to nationalistic, religious, ethnic or socio-economic indoctrination and incitement, which have reached him obliquely, through the media or the Internet – (blogs, Web sites, chat rooms, Facebook and other social networking sites) – or directly, through his immediate social circle – (spiritual mentors or leaders, teachers, relatives, peers).Although the politically motivated lone wolf may attack in response to a concrete event, his decision to do so is usually not a momentary caprice; rather, it is most often the culmination of a process of radicalization, involving continuous exposure to agitation and encouragement.It is worth noting that organized terrorism is usually more sophisticated and complex than personal initiative terrorism, and therefore often causes many more casualties.This is unsurprising, given that terrorist organizations have greater capability, resources and experience than does any individual attacker.However, terrorist organizations may fall prey to infiltration by intelligence agents.The multiplicity of people involved in the clandestine initiation, planning, preparation and execution of an organized terrorist attack creates a risk that information will leak out to security personnel, who may try to preempt the attack.In contrast, personal initiative attacks are usually less complex. The lone terrorist uses primitive means: “cold” weapons such as a knife or gun; vehicular attack, homemade, improvised explosive devices. While the number of casualties a lone attacker can cause is therefore more limited, the likelihood of thwarting his attack is also smaller.Because personal initiative attacks are perpetrated after an individual has made a very personal decision – one he has most likely not shared with even those closest to him – it is almost impossible to obtain early intelligence regarding his intentions.Those who are now tasked with investigating the terrorist attack at the 2013 Boston Marathon must determine just what sort of attack it was. Was it an instance of organized terrorism, carried out by a local group or cell sent on a mission by an organization headquartered outside the US? Or was it the personal initiative of a lone wolf or a local network unaffiliated in any way with – even if influenced by – a particular terrorist organization? It is too soon to know.However, if we assess the slivers of information already available, it appears the attack was conducted using small, improvised explosive devices, and that the two devices that exploded were placed very close to one another. We may therefore hazard a calculated guess that this terrible attack was the personal initiative of a local group or a lone wolf who, in this case, succeeded in fulfilling the dream of modern terrorists everywhere: to perpetrate an attack among a condensed crowd of people in the presence of a large media contingent.The chosen target – the finish line of the Boston Marathon – provided both of these key variables.Nevertheless, and despite the immense importance of this event to sports enthusiasts from around the world, the Boston Marathon is a local event. The residents of other US states and other countries may barely be aware of this marathon. It is not an international event commensurate with, say, the Olympics. It did not take place at a famous, symbolic site like the World Trade Center or the Empire State Building in New York, or the Pentagon in Washington, DC. This also suggests that the initiative was local, whether the attack itself was perpetrated by a lone wolf, by a limited network not tied to an established terrorist organization, or even by an independent sleeper cell affiliated with a local or international terrorist organization.A more decisive answer to these questions and, primarily, swift and precise identification of the specific nature and plan of this attack will promote an efficient investigation that will lead to the apprehension of all those involved. Clarification of the type and nature of this attack will also facilitate an examination of the functioning of security forces and the derivation of lessons whose implementation may reduce, or preclude, harm from similar terrorist events in the future.