March 16, 2014
Crack a Wi-Fi Network’s WEP Password with BackTrack
What
You'll Need
Here's what you'll need:
Acompatible Wireless Adapter
This is the biggest requirement. You'll need a
wireless adapter that's capable of packet injection.
Download yourself a copy of the CD and burn it, or
load it up in VMware to get started.
ANearby WEP-Enabled Wi-Fi Network
The signal should be strong and ideally people are
using it, connecting and disconnecting their devices from it. The more use it
gets while you collect the data you need to run your crack, the better your
chances of success.
Patiencewith the command line
Wi-Fi hacking process that requires typing in long,
arcane commands and waiting around for your Wi-Fi card to collect data in order
to crack the password.
To crack WEP, you'll need to launch Konsole,
BackTrack's built-in command line.
First run the following to get a list of your
network interfaces:
airmon-ng
The only one I've got there is labeled ra0. Yours
may be different; take note of the label and write it down. From here on in,
substitute it in everywhere a command includes (interface).
Now, run the following four commands. See the output
that I got for them in the screenshot below.
airmon-ng stop (interface)ifconfig
(interface) downmacchanger
--mac 00:11:22:33:44:55 (interface)airmon-ng
start (interface)
If you
don't get the same results from these commands as pictured here, most likely
your network adapter won't work with this particular crack. If you do, you've
successfully "faked" a new MAC address on your network interface,
00:11:22:33:44:55.
airodump-ng (interface)
To see a
list of wireless networks around you. When you see the one you want, hit Ctrl+C
to stop the list. Highlight the row pertaining to the network of interest, and
take note of two things: its BSSID and its channel (in the column labeled CH),
as pictured below. Obviously the network you want to crack should have WEP encryption
(in the ENC) column, not WPA or anything else.
Like I
said, hit Ctrl+C to stop this listing. Once you've got it, highlight the BSSID
and copy it to your clipboard for reuse in the upcoming commands.
Now we're going to watch what's going on with that network you chose and capture that information to a file. Run:
airodump-ng -c (channel) -w (file name) --bssid (bssid) (interface)
Where
(channel) is your network's channel, and (bssid) is the BSSID you just copied
to clipboard. You can use the Shift+Insert key combination to paste it into the
command. Enter anything descriptive for (file name).
You'll get
output like what's in the window in the background pictured below. Leave that
one be. Open a new Konsole window in the foreground, and enter this command
aireplay-ng -1 0 -a (bssid) -h
00:11:22:33:44:55 -e (essid) (interface)
Here the
ESSID is the access point's SSID name, which in my case is yoyo. What you want
to get after this command is the reassuring "Association successful"
message with that smiley face.
aireplay-ng -3 -b (bssid) -h 00:11:22:33:44:55 (interface)
Here we're
creating router traffic to capture more throughputs faster to speed up our
crack. After a few minutes, that front window will start going crazy with
read/write packets. Basically you want to wait until enough data has been
collected to run your crack. Watch the number in the "#Data"
column—you want it to go above 10,000. (Pictured below it's only at 854.)
Depending
on the power of your network this process could take some time. Wait until that
#Data goes over 10k, though—because the crack won't work if it doesn't. In
fact, you may need more than 10k, though that seems to be a working threshold
for many.
Once you've collected enough data, it's the moment
of truth. Launch a third Konsole window and run the following to crack that
data you've collected:
aircrack-ng -b (bssid) (file
name-01.cap)Here the filename should be whatever you entered above for (file name). You can browse to your Home directory to see it; it's the one with .cap as the extension.
If you didn't get enough data, aircrack will fail and tell you to try again with more. If it succeeds, it will look like this:
The WEP key appears next to "KEY FOUND." Drop the colons and enter it to log onto the network.
