This chapter illustrates the key concepts of security, wireless networks, and security over wireless networks. Wireless security is demonstrated by explaining the main specifications of the common security standards like 802.11 WEP, 802.11 WPA, WPA2 (802.11i) and Bluetooth security standards. Moreover, it explains the concept of WMAN (Wireless Metropolitan Access Network) and its security specifications. Finally, it sums up with thoughts and suggestions about wireless security, along with chosen examples of the current proposals in wireless security.