Terrorism, an issue of interest to all States, has been on the international agenda for decades. Today, the speed and scale at which the gravity of the terrorist threat is evolving require coordinated efforts and multidisciplinary actions. Many extremists groups are emerging and shaping alliances, and often converging with criminal networks managing to traffic in drugs, persons, and firearms. The extent of the recent flow of foreign terrorist fighters to a number of conflict situations is unprecedented and increasingly representing a threat to peace, democracy, and security, posing many new challenges to the international community. Foreign terrorist fighters have multifarious backgrounds and have a variety of different motivations and objectives. The only common denominator between them is that they represent a threat without borders. Research has shown that prisons can provide an environment where convicted terrorists can network, compare and exchange tactics, radicalize and recruit new members, and command and control operations outside the prison. However, where rehabilitation programs are properly employed, prisons also offer the setting to enable a reversal of radicalization and thus can play a crucial role in the fight against terrorism. A historic milestone in addressing terrorism was reached in 2006 with the Global Counter-terrorism Strategy. For the first time, all Member States of the United Nations agreed on a global strategy to coordinate their counter-terrorism efforts. There is a growing global consensus on the fact that terrorists cannot be defeated or rehabilitated without interventions addressing the root of the problem – the specific ideologies and motivations that stimulate alarming levels of recruitment into these criminal organizations. However, research and experience confirm that there is no single approach which is effective or appropriate for all violent extremists. As such, in order to counter the phenomenon, there is a need to build tailored strategies which integrate cultural, sociological and context-specific considerations and draw on the expertise of all relevant stakeholders, including State agencies and civil society organizations, absorbing international best practices and proven methodologies.