Perhaps one of the most puzzling and unpredictable forms of terrorism is provided by violent acts committed by a single individual. These so-called lone wolves are a nightmare for the police and intelligence community as they are extremely difficult to detect and to defend against. Compared to group terrorism or network-sponsored terrorists, lone operators have a critical advantage in avoiding identification and detection before and after their attacks, since most of them do not communicate with others with regard to their intentions. Although lone wolves might have the disadvantage of lacking the means, skills, and “professional” support of terrorist groups, some of them nonetheless have proven to be very lethal., Infamous examples from the United States, Israel and Europe include Baruch Goldstein, an American-born Israeli citizen who was responsible for the death of 29 Muslims praying in the Cave of the Patriarchs in Hebron, the Austrian Franz Fuchs, who used letter bombs to kill 4 and injure 15 people, US army major Nidal Malik Hasan, who is accused of a mass shooting at Fort Hood in which 13 people died and 30 were wounded, and the American mathematician Theodore Kaczynsky, also known as the “Una Bomber”, who engaged in a mail bombing spree that killed three and wounded 23., In this paper, we investigate these different types of perpetrators and the possible increase of lone wolf terrorism due to mounting appeals in Islamist circles to strike against the West as a lone operator. In addition, we look into the challenge of countering lone wolf terrorism and map out possible responses to prevent attacks – responses that at the same time respect fundamental freedoms and civil liberties.