Wireless networks are throwing up a lot of challenges. Though on the surface they appear to be network management challenges, they are security concerns as well. Malicious intruders can perpetrate several kinds of attacks in a WLAN.

Sniffing: This term is used when network traffic is monitored, legitimately or otherwise. Most information transmitted by access points is easy to sniff because it is in plain text mode and completely unprotected. Once the intruders have vital data about the security setup of a WLAN, they can very easily impersonate authorized
network users to steal enterprise information.

Spoofing: This is where an intruder impersonates legitimate devices on the network by stealing credentials. For example, the intruder first sniffs the wireless traffic and captures the valid MAC address of a legitimate wireless device on the WLAN, which is then used to make the access point think he or she is an authorized user.

Jamming: This activity involves introducing interfering radio signals that render the access points incapable of transmitting any wireless information. The wireless signals are 'jammed' and any business activity requiring wireless communication is disturbed. 802.11b WLANs are easily jammed-intentionally or otherwise-due to the crowded frequency band in which they operate.

Session hijacking: Here an intruder makes a legitimate user believe (who is connected with the access point) that he or she has been disconnected. In the meantime, the intruder connects with the still active WLAN connection, leaving both the network administrator and the user 'in the dark'.

Denial of service: Once the intruders get on to the network, they can easily flood the WLAN with useless traffic, which will eventually cause the WLAN to shutdown. This can be done in several ways, including constant requests to login to the WLAN even after the request has been approved.

Man in the middle: In this case, the intruder changes the configuration of his or her wireless device so that it resembles a wireless access point. All traffic from an authorized user's device is then forced to travel through this rogue device, which acts like a pseudo-router. In this manner, the intruder is able to view all the user's credentials, without him or her being aware, and then become a real user on the WLAN. This attack is made possible because WLAN specifications only provide client-side authentication. Access point authentication is not available by default, so there is no way for the client to be sure that the user is connected to a legitimate access point.

Source: CA