The book "Detection of Intrusions and Malware, and Vulnerability Assessment" is a collection of expert contributions presented at the 13th International Conference on this topic in 2016 in San Sebastián, Spain. It includes 19 revised full texts and 2 extended abstracts selected from a total of 66 submitted papers. The contributions provide a comprehensive overview of the current state of the art in the fields of intrusion detection, malware analysis, and vulnerability assessment. The topics covered range from novel ideas and techniques to applications in key areas of computer security, including vulnerability detection, attack prevention, web security, and malware detection and classification. The authors, including Juan Caballero and Urko Zurutuza, contribute their expertise to deepen the understanding of these critical areas of IT security.