This book constitutes the revised selected papers of the 4th International Conference on Information Systems Security and Privacy, ICISSP 2018, held in Funchal - Madeira, Portugal, in January 2018. The 15 full papers presented were carefully reviewed and selected from a total of 71 submissions. They are dealing with topics such as data and software security; privacy and confidentiality; mobile systems security; biometric authentication; information systems security and privacy; authentication, privacy and security models; data mining and knowledge discovery; phishing; security architecture and design analysis; security testing; vulnerability analysis and countermeasures; web applications and services.