After re-installing the OS on a Dell Powervault 715n, I remembered that out of the box, it won’t connect to Windows Update (which is of course really, really stupid for a Windows 2000 Server based NAS).
If you RDC into the box, and then try to connect to Windows Update, you’ll see a message like this:
Access Denied
Network policy settings prevent you from using Windows Update to download and install updates on your computer.
If you believe you have received this message in error, please check with your system administrator.
Solution
To get around this on the 715N, follow these instructions:
Log in as Administrator
Go Start > Run… > gpedit.msc
In the Left pane: Open User Configuration, Administrative Templates, and then click Start Menu and Taskbar
In the Right pane: Double-click on Disable and remove links to Windows Update
Choose ‘Disable’ and click OK
You can now get Windows Updates via the Start Menu
Every time you deploy a WEP Access Point, a fluffy kitty dies.
Primer
Recently a team of German cryptography researchers perfected methods to recover a WEP key faster than ever before. The older Weak IV attacks generally needed between 500,000 and 2,000,000 packets to recover a 128-bit WEP key. In contrast, the new PTW method needs a mere 85,000 packets to have a 95% chance of recovering the WEP key.
Unlike the Weak IV attack, instead of collecting weak IVs, the PTW method collects ARP requests and responses to attack the encryption. ARP requests can either be collected naturally, or can be generated via packet injection. Until recently, packet injection was only possible in Linux. With the advent of the AirPcap USB adapter, and some unsupported beta drivers, it’s possible to inject packets in Windows. Update: CACE have released AirPcap Tx, which features fully supported packet injection, for an added premium.
In this tutorial, I’ll guide you through the process of recovering a WEP key, via the PTW attack, in Windows. For this you’ll be using the AirPcap USB adapter, Cain, aircrack-ptw, and the aircrack-ng suite.
Legalities
It’s important to point out that these methods should only be applied with permission from the owner of the target AP. You should either be auditing, penetration testing, or demonstrating the weaknesses of WEP in a Test Lab environment. You should not be using these methods to get “Free internet”!
Preparation
You’ll need:
An AP configured with WEP
At least one client associated with the Access Point (to give us an initial ARP request)
Install the beta drivers (or if you have AirPcap Tx, install the drivers from the CD-ROM)
Plug in the AirPcap
Install Cain
Extract aircrack-ng to c:\airpcap\
Extract aircrack-ptw to c:\airpcap\
Move aircrack-ptw.exe to the bin folder (this is no longer required - see my notes)
Optional: To make things easier, move the contents of the bin folder to c:\airpcap\. You’ll then be able to run aircrack-ptw.exe with just c:\airpcap\aircrack-ptw.exe mycapture.cap
Let’s get cracking
I added narration to the video this evening at 20:36. It’s my first attempt at narration, and a little noisy, but I’m sure things will improve as time goes on!
The primary counter measure to this WEP attack is to cease using WEP and switch your Access Points to WPA encryption. As you’ve seen in this video, WEP is just too easy to crack. For further reading, Wikipedia has an excellent entry on WPA.
Access Points are so cheap now that, if your AP doesn’t support WPA via a firmware upgrade, you can easily afford a new one with full WPA or WPA2 support.
Notes
Note 1: After recording this tutorial, I’ve become aware that, as of version 0.9, aircrack-ng.exe natively supports the PTW attack by using the -z switch. For example: aircrack-ng.exe -z mycapturefile.cap. If you want to use this attack, download aircrack-ng from the authors, and replace aircrack-ng.exe in c:\airpcap with the new one.
Note 2: The whole process from starting capture to recovering the WEP key takes about 10 minutes.
Note 3: It is important that you get the Packet Injection drivers and the aircrack-ng release specifically for the AirPcap adapter, or this will not work.
Note 4: Just to summarise the steps in the video:
Run Cain and passively scan for the target AP, making a note of the Channel number.
Using the channel number, tell AirPcap to inject packets once it has collected an ARP request. (You can sometimes force an ARP by sending Deauth. To do that, right click on the client. Otherwise, repair the Wireless connection on the client connected to the AP)
To use the PTW attack, you need to collect all packets. By running airodump-ng you can collect all the packets generated by Cain. The reason we use airodump-ng instead of Cain, is that Cain only collects WEP IVs.
Once you’ve collected enough packets, run aircrack-ptw against the capture file.
As of version 0.9, the aircrack-ng suite natively supports the PTW attack. Download it here. To invoke the PTW attack in aircrack-ng, run it with the -z switch: aircrack-ng.exe -z mycapturefile.cap.
A French chap has compiled Aircrack-PTW for Windows. This is great for anyone using the AirPcap adapter to inject packets in Windows, as the new PTW attack dramatically reduces the amount of packets you need to collect before attempting to crack the WEP key. Notice in the screenshot below, only 83,000 packets were needed to break a 128bit key; as opposed to around 400,000 with the KoreK attack.
The executable is in French but it’s still perfectly usable; All you’re looking for is the WEP key!
Just run it with:
aircrack-ptw.exe yourcapturefile.cap
When I get some time I’ll try to compile a version in English, but for now you can grab the French version: Download Aircrack-PTW for Windows.
I’m in the process of writing up and recording a demonstration of cracking WEP in Windows with AirPcap, Cain, and aircrack-ptw. Expect to see something within a week! Update: Check it out here
Note: It is possible to get this working by using the cheaper “Classic” AirPcap, in conjunction with the old 2.0 Beta Tx Drivers for AirPcap, to enable packet injection capability, but this is entirely unsupported, and is not guaranteed to work. YMMV.
Notes
To begin ARP injections, AirPcap must capture at least 1 ARP request from a system on the target AP. You can usually force this by sending a Deauth to a connected client.
Make sure you have over 250,000 IVs before attempting to crack the WEP key.
In my tests, the old AirPcap (silver-grey) appears to perform significantly faster than the new AirPcap (dark-grey). I think it’s about 10x faster.
Phil is an IT Professional working at DisplayLink in Cambridge,
England. He generally blogs about useful solutions that he comes across in his work/play.
