Computer System Security: Basic Concepts and Solved Exercises is designed to expose students and others to the basic aspects of computer security. Written by leading experts and instructors, it covers e-mail security; viruses and antivirus programs; program and network vulnerabilities; firewalls, address translation and filtering; cryptography; secure communications; secure applications; and security management. Written as an accompanying text for courses on network protocols, it also provides a basic tutorial for those whose livelihood is dependent upon secure systems. The solved exercises included have been taken from courses taught in the Communication Systems department at the EPFL. .