Hack a wi-fi network with WEP security

1) First we need to scan for available wireless networks.

Theres this great tool for windows to do this.. called “NetStumbler” or Kismet for Windows 
and Linux and KisMac for Mac.

The two most common encryption types are:

1) WEP

2) WAP

WEP i.e Wire Equivalent Privacy is not consideres as safe as WAP 

i.e Wireless Application Protocol.

WEP have many flaws that allows a hacker to crack a WEP key easily.. whereas

WAP is currently the most secure and best option to secure a wi-fi network..

It can’t be easily cracked as WEP because the only way to retreive a WAP key is to use 
a brute-force attack or dictionary atack.

Here I’ll tell you how to Crack WEP

To crack WEP we will be using Live Linux distribution called BackTrack to crack WEP.

BackTrack have lots of preinstalled softwares for this very purpose..

The tools we will be using on Backtrack are:

Kismet – a wireless network detector

airodump – captures packets from a wireless router

aireplay – forges ARP requests

aircrack – decrypts the WEP keys

1) First of all we have to find a wireless access point along with its bssid, essid and 
channel number. To do this we will run kismet by opening up the terminal and typing in 
kismet. It may ask you for the appropriate adapter which in my case is ath0. You can 
see your device’s name by typing in the command iwconfig.

2) To be able to do some of the later things, your wireless adapter must be put into 
monitor mode. Kismet automatically does this and as long as you keep it open, your 
wireless adapter will stay in monitor mode.


3) In kismet you will see the flags Y/N/0. Each one stands for a different type of 
encryption. In our case we will be looking for access points with the WEP encryption. 
Y=WEP N=OPEN 0=OTHER(usually WAP).


4) Once you find an access point, open a text document and paste in the networks 
broadcast name (essid), its mac address (bssid) and its channel number. To get the 
above information, use the arrow keys to select an access point and hit <ENTER> 
to get more information about it.

5) The next step is to start collecting data from the access point with airodump. 
Open up a new terminal and start airodump by typing in the command:
airodump-ng -c [channel#] -w [filename] –bssid [bssid] [device]
In the above command airodump-ng starts the program, the channel of your access 
point goes after -c , the file you wish to output the data goes after -w , and the MAC 
address of the access point goes after –bssid. The command ends with the device 
name. Make sure to leave out the brackets.


6) Leave the above running and open another terminal. Next we will generate some 
fake packets to the target access point so that the speed of the data output will 
increase. Put in the following command:
aireplay-ng -1 0 -a [bssid] -h 00:11:22:33:44:55:66 -e [essid] [device]
In the above command we are using the airplay-ng program. The -1 tells the program 
the specific attack we wish to use which in this case is fake authentication with the 
access point. The 0 cites the delay between attacks, -a is the MAC address of the 
target access point, -h is your wireless adapters MAC address, -e is the name (essid) 
of the target access point, 
and the command ends with the your wireless adapters device name.


7) Now, we will force the target access point to send out a huge amount of packets that 
we will be able to take advantage of by using them to attempt to crack the WEP key. 
Once the following command is executed, check your airodump-ng terminal and you 
should see the ARP packet count to start to increase. The command is:
aireplay-ng -3 -b [bssid] -h 00:11:22:33:44:5:66 [device]
In this command, the -3 tells the program the specific type of attack which in this case is
packet injection, -b is the MAC address of the target access point, -h is your wireless 
adapters MAC address, and the wireless adapter device name goes at the end.
 Once you have collected around 50k-500k packets, you may begin the attempt to break 
the WEP key. The command to begin the cracking process is:
aircrack-ng -a 1 -b [bssid] -n 128 [filename].ivs
In this command the -a 1 forces the program into the WEP attack mode, the -b is the 
targets MAC address, and the -n 128 tells the program the WEP key length. If you don’t 
know the -n , then leave it out. This should crack the WEP key within seconds. The more 
packets you capture, the bigger chance you have of cracking the WEP key.