Observers note the attacks are a relatively rare type of terrorist attack but have been increasing in number, and that it is sometimes difficult to tell whether an actor has received outside help and what appears to be a lone wolf attack may actually have been carefully orchestrated from outside.
The term "lone wolf" was popularized by white supremacists Alex Curtis and Tom Metzger in the 1990s. Metzger advocated individual or small-cell underground activity, as opposed to above-ground membership organizations, envisaging "warriors acting alone or in small groups who attacked the government or other targets in 'daily, anonymous acts.'"
Terrorism expert Brian Michael Jenkins of the RAND Corporation prefers the term stray dog to lone wolf. According to Jenkins, most individuals involved in such attacks "skulk about, sniffing at violence, vocally aggressive but skittish without backup". Though these individuals seem to be acting alone, there are often ties between lone wolves and terrorist organisations for example, terrorist backed online content.
The term "lone wolf" is used by US law enforcement agencies and the media to refer to individuals undertaking violent acts of terrorism outside a command structure. The FBI and San Diego Police's investigation into the activities of a self-professed white supremacist, Alex Curtis, was named Operation Lone Wolf, "largely due to Curtis' encouragement of other white supremacists to follow what Curtis refers to as 'lone wolf' activism".
The term lone wolf is used to distinguish terrorist actions carried out by individuals from those coordinated by large groups. Terrorist attacks that are carried out by small cells are not classified as lone wolf attacks. Lone wolf attacks are far more rare than attacks carried out by groups. Since 1940, there have only been around 100 successful lone wolf attacks in the United States. The number of attacks is increasing, however, and has grown each year since 2000. Lone wolves generally come from different demographics than far right attackers as well. As compared to those on the far right, lone wolf attackers who become inspired by al-Qaeda and ISIS tend to be younger and better educated. According to studies, lone wolves have more in common with mass murderers than they do with members of the organized terrorist groups that often inspire them.