Virtual High Five for Wireless Field Day 5!

WFD-Logo1-wpcf_400x398With just over a week to Wireless Field Day 5 I wanted to say thank you to Stephen Foskett (@sfoskett) and the Wireless Field Day crew. I was so honored when asked about attending Wireless Field Day 5 and have been totally impressed with the planning, communication, and organization of the event. Stephen and crew have worked hard to plan so many of the details I feel my only responsibility is making the flight and bringing some extra clothes!

To increase my excitement for WFD5 I have checked out blog posts from past WFD attendees and they really paint a picture of the events being nothing short of excellent with great people coming together to share their technical knowledge.

One such article, “The Value of Tech Field Day” by @pandom_ has circulated on Twitter this past week.

I have never personally met the other delegates, but have run across or had conversations with most if not all of them through social media. I do consider the other delegates the “rock stars” of the wireless world and really look forward to meeting them and talking wireless, but mostly learning as much as I can cram into my memory!

Stephen and crew have also set up a great lineup of vendor presentations and since I first saw the lineup 2 or 3 more vendors were added, and at last glance there are 9 vendors presenting at the conference!

Between rubbing elbows with the other delegates and seeing the vendor presentations I will be on information overload and I wish I could stick a USB drive in my ear to help bring home the material and knowledge I’m sure to learn.

Thanks to Stephen, the WFD5 crew, the other delegates, and the vendors! Being a Wireless Field Day newbie everyone has been tremendous and made me feel welcome and already part of the Wireless Field Day family!

Thank You! Dale

Any one wanting to check out the list of delegates along with the vendor presentation schedule can visit the Wireless Field Day 5 website, and the event can be followed on Twitter with the #WFD5 hash tag.

Cracking WPA using Fern WiFi Cracker

Note: For this demo I’m using a lab environment network that is not routed to the internet. I will be using the Fern WiFi Cracker open source wireless security tool included in the Kali Linux and Backtrack 5 r3 security distros. Before attempting to use Fern or any other utility in Kali or Backtrack please make sure to read the help and MAN pages for a complete description of the program options and switches. This demo is for wireless pentesting educational purposes and to emphasize the insecurities of using a weak or common dictionary word for wireless network authentication and encryption security key or passphrase.

Fern Wi-fi Cracker can crack WEP, WPA, and WPA2 secured wireless networks. Fern basically takes the command line utilities to crack these networks and puts them in a GUI. Very simple to use… scary easy! Fern also provides some extra functionality for hijacking sessions and locating a computers geolocation via its Mac address, but I have not tested with these features.

For this demo I will be using Backtrack 5 r3 running in VMware Workstation on a Win 7 host.

Originally I was using Fern in Kali and ran into some issues with my wireless adapter and with the program freezing or not opening after updating it. I have the fixes I discovered in another blog post for anyone else that may have these same problems.

Router Setup

I’m using an old Cisco/Linksys 802.11g wireless router for this demo and all the settings are defaulted except the security settings, which I set to WPA Personal with a Shared Key passphrase of “password”. The word password should never be used for a real password or passphrase and I’m using it here since I know the Fern program will quickly crack it. In real world situations a WPA/WPA2 passphrase should be completely random and not a common dictionary word. For help on creating a secure WPA/WPA2 passphrase please read my earlier blog post.


Setup the Wireless Adapter

Plug in the USB wireless adapter (I’m using the Alfa AWUS036H 802.11b/g USB wireless adapter) and open the Terminal and run iwconfig to verify the USB adapter interface.


On occasions I have had to bring the wireless adapter interface up using the following command.

#ifconfig wlan0 up

Starting the Fern Program

To start Fern from the Terminal type in the following commands

#cd /pentest/wireless/fern-wifi-cracker

or start Fern via the GUI using the Backtrack menu

Applications/Backtrack/Exploitation Tools/Wireless Exploitation Tools/WLAN Exploitation/fern-wifi-cracker

Using the Fern Program

Select the Interface and Fern enables monitor mode. If your wireless interface does not show in the list hit the Refresh button and try again.


Before starting the scan double-click on any blank area of the Fern home screen to bring up the Access Point Scan Preferences screen. You can set the channel option to scan a single channel or leave it at the default All Channels. One nice feature is to check the Enable XTerms option which will have Fern open up the Terminal windows during its usage to see what the program is doing in the background. Click OK when done.


Back on the Fern home screen click the Scan for Access points button.


Two Terminal windows will open; one showing the WEP enabled networks (no screen shot), and another showing the WPA enabled networks. The top part of the WPA Scan Terminal window shows the networks being found, and the lower part shows any connected client devices. For a WPA attack to work it requires a connected client. The most important part of the attack will kick the client off the wireless network and capture the 4-way handshake when the client device re-authenticates to the network. If the network you want to pentest has no connected client your out of luck!


On Ferns home screen the networks being detected will start populating next to the WiFi WEP or WiFi WPA buttons. (I have been seeing less and less WEP enabled networks, so that is a good thing!)


Clicking on the WiFi WEP or WiFi WPA button will bring up the Attack screen and the top pane will list the networks found. Select the AP to crack, but before clicking the Attack button to the right let’s go over a couple of settings.


I will use the Regular Attack option, but there is a WPS Attack option and I believe Fern uses the Reaver utility to launch the WPS attack. You can read more about Reaver by clicking here.

Common.txt is the wordlist that comes with the Fern program, but any wordlist you download or have created on your own can be used by hitting the Browse button and pointing Fern to the alternative wordlist file.


With the Regular Attack and the wordlist selected hit the Attack button.


Fern will start the attack and on the left side of the screen the attack steps will turn yellow as Fern works through the various steps. The most important step is capturing the 4-way handshake and Fern will open an aireplay-ng Terminal window showing the progress of deauthentication (if XTerms is checked in the preferences) of the connected client.


It may take several attempts to deauth a client and capture the 4-way handshake.


Once Fern has captured the handshake it will start the bruteforce attack. Viola! If the WPA key is in the wordlist being used it will display the found key in Red.


As I mentioned I setup a passphrase I knew would be found quickly, and from start to finish this attack took under 4 minutes!

Back on the Fern main screen is a Key Database button and it now shows one entry.


Clicking the Key Database button will display the found keys.



Using a common dictionary word for a WPA or WPA2 passphrase makes it easier to hack with utilities like Fern. The Fern utility is free to download and simple to use, and not everyone is going to use it for legit wireless pentesting purposes.

With possession of the WPA key a person can associate to network and have a gateway to the internet, or they could launch other attacks. For example, with possession of the WPA key the attack could be expanded to include decryption of the data traffic of the legitimate clients on the wireless network.

Thanks for reading and stay wireless secure!

Fern WiFi Cracker Maintenance and Support

Some support issues and other odd things I have researched while using the Fern WiFi Cracker program on Kali Linux and/or Backtrack 5.

Installing Fern

I’m not sure what version of Backtrack started including Fern, but to install the program use the following command.

# apt-get install fern-wifi-cracker

Issue #1: When I started using Fern the program locked up or froze, and updating the program seemed to fix the issue. There are times when the program seems to not respond after clicking on buttons, but after a few seconds it starts working.

After starting Fern look in the lower left corner to see if any updates are available. An internet connection is required to check for and download any updates. Click the update button to download and install the update.


Fern will show the progress.


Restart of the Fern program.


The Fern program will report no more available updates.


Issue #2: After updating Fern the program would not open and running this command fixed the issue. (I only experienced this with Kali and not in any of the Backtrack 5 distros)

#chmod +x /usr/share/fern-wifi-cracker/

I found the above fix in this discussion thread with a Google search.

Wireless Adapter Issues in Kali

If you’re getting the SIOCSIFFLAGS (see screen shot below) error message when bringing up your wireless adapter run the following commands.

#rmmod rtl8187
#rfkill block all
#rfkill unblock all
#modprobe rtl8187
#rfkill unblock all
#ifconfig wlan0 up


I discovered that if I shutdown or restart Kali the error does show up again with the next login. You can read more on this post about the error and creating a batch file to run all the commands at the same time.

General Wireless Troubleshooting Help on the Kali Support Site

If you’re having issues with your wireless adapter check the Kali support documentation or do some Google searches. I found a lot of good information on the internet. Good luck and happy pentesting!