Security has become a primary concern in order to provide protected communication in Wireless as well as wired environment. In my book we analyze the security issue in Ad-Hoc network as well as infrastructure Networks. Unlike the wire line networks, the unique characteristics of mobile ad hoc networks pose a number of nontrivial challenges to security design, such as open peer-to-peer network architecture, shared wireless medium, stringent resource constraints, and highly dynamic network topology. In this book the investigations have been carried out with the following main objectives: • To investigate the performance Comparison of Routing Protocols for Security Issue in Wireless Mobile Ad Hoc Networks. • To demonstrate the Comparison of Intelligent Jamming in RF (Physical) Layer with WLAN Ethernet Router and WLAN Ethernet Bridge. • To investigate Security Comparison of Wired and Wireless Network with Firewall and Virtual Private Network (VPN).All the above work has been accepted by good standardization one of the works has accepted by ITU-T(International Telecommunication Union)and i have received Young author award for the same.