This book constitutes the refereed proceedings of the 6th International Conference on Detection of Intrusions and Malware, and Vulnerability Assessment, DIMVA 2009, held in Milan, Italy, in July 2009. The 10 revised full papers presented together with three extended abstracts were carefully selected from 44 initial submissions. The papers are organized in topical sections on malware and SPAM, emulation-based detection, software diversity, harnessing context, and anomaly detection.