 to connect to the network and make free use of resources such as an Internet connection. Wireless LAN Security Threats The type of security threats faced by a wireless LAN are many and varied, and although initially targeted at the PHY and MAC layers, the ultimate goal is to access or disrupt data or activity at the application layer. A few of the main vulnerabilities are described below. Denial of service (DoS) attacks - an attacker floods a network device with excessive traffic, preventing or seriously slowing Wireless LAN Security normal access. This can be targeted at several levels, for example, flooding a web server with page requests or an access point with association or authentication requests. Jamming - a form of DoS in which an attacker floods the RF band with interference, causing WLAN communication to grind to a halt. In the 2.4 GHz band this could be done using Bluetooth devices, some cordless phones or a microwave oven! Insertion attacks - an attacker is able to connect an unauthorised client station to an access point, either because no authorisation check was made or because the attacker masqueraded as an authorised user. Replay attack - an attacker intercepts network traffic, such as a password, and uses it at a later time to gain unauthorised access to the network. Broadcast monitoring - in a poorly configured network if an access point is connected to a hub rather than a switch, the hub will broadcast data packets that may not be intended for wireless stations, and these can be intercepted by an attacker. ARP Spoofing (or ARP cache poisoning) - an attacker can trick the network into routing sensitive data to the attacker's wireless station, by accessing and corrupting the ARP cache in which MAC and IP address pairs are stored. Session hijacking (or man-in-the-middle attack) - a type of ARP spoofing attack in which an attacker breaks a station's connection with the access point, by posing as the station and disassociating itself, and then poses as the access point to get the station to associa