Tuesday, 25 July 2017

Cracking The WEP Key With Backtrack 5

As announced before we would be writing related to wifi attacks and security, This post is the second part of our series on wifi attacks and Security, In the first part we discussed about various terminologies related to wifi attacks and security and discussed couple of attacks. This post will also show you how one can easily crack WEP keys in no time.

Security Issues With WEP

WEP (Wired Equivalent Privacy) was proved full of flaws back in 2001, WEP protocol itself has some weakness which allows the attackers to crack them in no time. The biggest flaw probably in a WEP key is that it supports only 40bit encryption which means that there are 16million possibilities only.

For more information on WEP flaws, kindly read the WEP flaws section here.

Requirements :-

Here is what you would require to crack a WEP key:

1. Backtrack or any other Linux distro with aircrack-ng installed

2. A Wifi adapter capable of injecting packets , For this tutorial I will use Alfa AWUS036H which is a very popular card and it performs well with Backtrack

You can find compatible wifi card lists here.

Procedure :-

First Login to your Backtrack / Linux distro and plug in your Wifi adpter , Open a new konsole and type in the following commands

ifconfig wlan0 up

where wlan0 is the name of the wireless card ,it can be different .To see all wireless cards connected to your system simply type in " iwconfig ".

Putting your WiFi Adapter on Monitor Mode

To begin, you�ll need to first put your wireless adapter into monitor mode , Monitor mode is the mode whereby your card can listen to every packet in the air , You can put your card into monitor mode by typing in the following commands

airmon-ng start (your interface)

Example :- airmon-ng start wlan0

Now a new interface mon0 will be created , You can see the new interface is in monitor mode by entering "iwconfig mon0" as shown

Finding a suitable Target

After putting your card into monitor mode ,we need to find a network that is protected by WEP. You can discover the surrounding networks by entering the following command

airodump-ng mon0

Bssid shows the mac address of the AP, CH shows the channel in which AP is broadcasted and Essid shows the name broadcasted by the AP, Cipher shows the encryption type ,

Now look out for a wep protected network In my case i�ll take �linksys � as my target for rest of the tutorial

Attacking The Target

Now to crack the WEP key youll have to capture the targets data into a file, To do this we use airodump tool again, but with some additional switches to target a specific AP and channel. Most importantly, you should restrict monitoring to a single channel to speed up data collection, otherwise the wireless card has to alternate between all channels .You can restrict the capture by giving in the following commands

airodump-ng mon0 --bssid -c (channel ) -w (file name to save )

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