When examining techniques for sniffing wireless traffic, there are two types of techniques available. The first is sniffing WLAN traffic while authenticated and connected to the target WLAN. In this instance, there is the ability to utilize a Man in the Middle attack in conjunction with tools such as Ettercap, which forces network traffic through our testing machine.
A second technique is sniffing all the wireless traffic that we can get from a specific wireless network and decrypting it with the WPA or WEP passcode. This may become necessary if we are attempting to limit our footprint by not connecting to the WLAN. By passively sniffing traffic and decrypting it later, we lessen the chance that we will be detected.