This book contains the proceedings of the Second European Conference on Computer Network Defence to take place in December 2006 at the School of Computing, University of Glamorgan, in the UK, and the Workshop preceding it. The theme of the conference is the protection of computer networks. The conference has drawn participants from national and international organisations. The following are a list of topics amongst those discussed: Computer Network Operations, Computer Network Attack, Network Application Security, Web Security, Vulnerability Management and Tracking, Network Forensics, Wireless and Mobile Security, Cryptography, Network Discovery and Mapping, Network Security, Intrusion Detection Systems, Incident Response and Management, Malicious Software, Network Architectures and Management, Legal and Ethical Issues. The papers presented include contributions from leading figures in the field and are a valuable source of reference for both researcher and practitioner.