Over the past several years, wireless LANs (WLANs) have gained tremendous popularity due to the user mobility and ﬂexibility they offer in accessing information. In addition, the cost of wireless networking equipment has dropped, and there have been signiﬁcant improvements in performance. The enormous ﬂexibility offered by WLANs, however, presents a number of potential security challenges. A WLAN transmits data using radio waves, which makes the transmission signal available to anyone within the range of the transmitter, posing a high security risk to wireless networks. In this chapter, we discuss the mechanisms used to protect the security of WLANs, along with other related issues. The section titled “802.11 Wireless Local Area Network” gives a brief introduction to the IEEE 802.11 WLAN standard. In the section titled “Attacks against Wireless Networks,” we describe different types of attacks against WLANs. In the section titled “WLAN Security Services,” we present wireless network security services with particular emphasis on the IEEE 802.11 privacy and authentication mechanism. In the section titled “Security Weaknesses in WEP,” we discuss a number of vulnerabilities that have been found in the Wired Equivalent Privacy (WEP) protocol. In the section titled “Enhancing WEP Security: The IEEE 802.1X Standard,” we discuss the IEEE 802.1X standard, which enhances WLAN security. The section titled “Using Biometrics for Enhanced Wireless Authentication” gives a brief introduction
to biometrics and illustrates how it can be augmented with wireless protocols to further increase the security of WLANs. In the section titled “Wi-Fi Protected Access (WPA) and the IEEE 802.11i Standard,” we brieﬂy describe the emerging WPA and IEEE 802.11i standards.