Terrorism, in all its manifestations, affects us all. The use of the Internet to further terrorist purposes disregards national borders, amplifying the potential impact on victims. By highlighting cases and best practices that respond to this unique challenge, the present publication has two aims: first, to promote a better understanding of the ways in which communications technologies may be misused in furtherance of acts of terrorism and, second, to increase collaboration among Member States, so that effective criminal justice responses to this transnational challenge can be developed.