This book constitutes the refereed proceedings of the 5th International Workshop on Visualization for Cyber Security held on September 15, 2008, in Cambridge, Massachusetts, USA, in conjunction with the 11th International Symposium on Recent Advances in Intrusion Detection (RAID). The 18 papers presented in this volume were carefully reviewed and selected from 27 submissions. Viz Sec research has focused on helping human analysts to detect anomalies and patterns, particularly in computer network defense. This year’s paper focus on bridging the gap between visualization and automation.