The AirPcap adapter is a USB device that when used in tangent with the AirPcap drivers and WinPcap libraries, allows pen-testers to monitor 802.11b/g traffic in Monitor mode. Monitor mode is similar to promiscuous mode, but the adapter is not associated with an access point and can monitor the raw 802.11 packets going over the air. The beta AirPcap 2.1 drivers also allow for packet injection, making for the faster collection of weak IVs. This tutorial will cover the basic setup of the AirPcap adapter with Wireshark, and how to use it to crack 128 bit WEP with Cain.