E-based systems are ubiquitous in the modern world with applications spanning e-commerce, WLANs, health care and government organisations. The secure transfer of information has therefore become a critical area of research, development, and investment. This book presents the fundamental concepts and tools of e-based security and its range of applications. The core areas of e-based security - authentication of users; system integrity; confidentiality of communication; availability of business service; and non-repudiation of transactions - are covered in detail. Throughout the book the major trends, challenges and applications of e-security are presented, with emphasis on public key infrastructure (PKI) systems, biometric-based security systems, trust management systems, and the e-service paradigm. Intrusion detection technologies, virtual private networks (VPNs), malware, and risk management are also discussed. Technically oriented with many practical examples, this book is suitable for practitioners in network security, as well as graduate students and researchers in telecommunications and computer science.