This book would serve as an ideal guide for B.E. B.Tech., B.S., B.Sc, B.C.A., undergraduate students of Computer Science and Engineering, Information Technology, Electronics and Communication Engineering who wish to take up projects on Network Security. Students pursuing postgraduate course in Science and Engineering, M.E., M.Tech., M.S., M.Sc., M.C.A. students will find this book useful for their projects. Research Scholars working in the area of Network Security, will find this book as a handy reference guide for their M.Phil., Ph.D. D.Sc., and other post-doctoral research works. Software Engineers and Hardware Analysts, involved in IT and ITES sector specifically on Network Security, would find this book as a useful resource. As a word of conclusion, we believe that the reader will find this book as a really helpful guide and a valuable source of information about Network Security.