Wireless Network Cracking

Aircrack-ng is an 802.11 WEP and WPA-PSK keys cracking program that can recover keys once enough data packets have been captured. It implements the standard FMS attack along with some optimizations like KoreK attacks, as well as the all-new PTW attack, thus making the attack much faster compared to other WEP cracking tools. In fact, Aircrack-ng is a set of tools for auditing wireless networks.
 
Few interesting readings
Cracking WEP with aircrack-ptw in Windows with AirPcap and Cain
AirPcap Related Stuffs
Aircrack/Aireplay-ng Under Packet Injection Monitor Mode in Windows
It is very easy to crack WEP based wireless network. So it is good that you use WPA for your wireless network.