As e-commerce becomes the norm of business transactions and information be­ comes an essential commodity, it is vital that extensive efforts be made to examine and rectify the problems with the underlying architectures, processes, methods, that are involved in providing and and tools, as well as organizational structures, utilizing services relating to information technology. Such a holistic view of the relevant structures is required in order to identify all of the key aspects that can affect network security. Unfortunately, today's systems and practices, although they have proved to be useful and become widespread, contain significant unnecessary complexity. This complexity provides many loopholes that make systems and practices vulnerable to malicious attacks by hackers as well as by individual and organized criminals. FUrther, there are enormous risks due to malfunction of the systems. The holes in the network system cannot simply be plugged up by the use of cryptography and firewalls. While many changes need to be made in operating systems and system software with respect to security, this alone does not solve the problem. The problems cannot be solved by addressing only a single key aspect of network security. A holistic approach is required. Sumit Ghosh has provided in this book such a holistic view of the area of network security. Thus, it is a most welcome contribution.