Here is a Python script by zx2c4.
With this script it is possible to crack a WEP WiFi network within minutes.
Please note all applications including aireplay-ng, airodump-ng, aircrack-ng and macchanger must be installed on the linux box. You can use the Backtrack 5 Penetration Testing Distribution with pre-installed cracking software. Backtrack 5 is available at: Offensive Security
Credits:
http://www.zx2c4.com/projects/wepautocrack/
#!/usr/bin/env python
#
# Copyright 2011 Jason A. Donenfeld. All Rights Reserved.
#
#
# ——— WEPAutoCrack ———-
# by zx2c4
# ———————————
#
# This utility terminates disruptive daemons, scans for networks,
# places your wifi card into monitor mode, switches to the right channel,
# fakes a random MAC address, and builds a “choose your own adventure”
# instruction sequence for the particular access point you choose to
# crack, for use with aircrack-ng for cracking WEP passwords, and finally
# resets your daemons once you’ve found a password.
#
# Be sure to look at the pwn() function. There are /etc/init.d/ commands in
# there to shutdown and startup your system’s networking services. Here you
# will find how I have my gentoo box setup, but you’ll likely need to
# change it to suit your own needs. It should be trivial — stopping and
# starting NetworkManager, if you use that, or whatever your situation
# is. There are two “CHANGE ME” blocks below. Find them. Edit them.
#
# greetz to gohu for iwlist parsing code at
# https://bbs.archlinux.org/viewtopic.php?pid=737357
#