The chapter discusses the importance of security information stored in modern electronic travel documents and its impact on terrorism. It highlights the various forms of terrorism, including small-scale attacks with low possibility of occurrence but high magnitude of consequences, as well as large-scale attacks causing mass casualties. The chapter also touches upon the role of lack of security measures, old readable travel documents' limitations, electronic travel documents' security features, border security's role in preventing unauthorized infiltration, and the International Civil Aviation Organization's (ICAO) involvement in security policy.