Finally, I’ve had time to write down my notes on using aircrack-ng with the Airpcap Tx adapter in Windows. Before you read on, please be aware that this isn’t meant to be a guide or tutorial, it’s just my notes. Thanky

Basics

Start capturing:

airodump-ng \\.\airpcap00 airpcap CHANNELNUMBER mycapturefile

Fake auth:

aireplay-ng --fakeauth 0 -e "MYSSID" -a BSSIDMAC -h AIRPCAPMAC \\.\airpcap00

Start attack:

aireplay-ng --arpreplay -b BSSIDMAC -h CLIENTMAC \\.\airpcap00

Deauth (if we need ARPs):

aireplay-ng –deauth 3 -a BSSIDMAC -c CLIENTMAC \\.\airpcap00

Start cracking:

aircrack-ng -z mycapturefile.cap

Worked example:

airodump-ng.exe \\.\airpcap00 airpcap 11 mycapturefile
aireplay-ng --fakeauth 0 -e "WEP" -a 00:a0:c5:9d:d5:50 -h 00:02:72:67:92:8a \\.\airpcap00
aireplay-ng --arpreplay -b 00:a0:c5:9d:d5:50 -h 00:90:4b:eb:9b:36 \\.\airpcap00
aireplay-ng --deauth 3 -a 00:a0:c5:9d:d5:50 -c 00:90:4b:eb:9b:36 \\.\airpcap00
aircrack-ng -z mycapturefile.cap

Download

I’ve prepared a special release of the aircrack-ng tools originally prepared by CACE Technologies on the AirPcap CDROM. It replaces the new aireplay-ng.exe with an older one which, in my tests, appears to perform better.

Download the release of aircrack-ng for AirPcap Tx

As a business you can’t use HyperTerminal Private Edition unless you pay a licence fee; and now that Microsoft has removed HyperTerminal from Windows Vista, finding an Open Source, free-for-commercial-use, replacement for HyperTerminal is invaluable for budget constrained IT departments.

Download PuTTY here

It also seems that Poderosa support Serial comms with a plugin, which I wasn’t aware of until reading this blog post.

What do you use instead of HyperTerminal? I’d love to hear about any programs I’ve missed!

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)
• A standard AirPcap Adapter with the unsupported beta packet injection driver or a fully-supported AirPcap Tx.
• Cain and Abel
• aircrack-ng for AirPcap
• aircrack-ptw for Windows

Now you’ll need to prepare the environment:

• 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!

Youtube Video Link

Countermeasures

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:

1. Run Cain and passively scan for the target AP, making a note of the Channel number.
2. 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)
3. 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.
4. 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

1. Start > Run… > services.msc
2. Find the Wireless Zero Configuration service.
3. Right click on it, and choose “Start”.

The Authentication tab will then appear on your Network connection properties.

Yes, I know. But apparently, to get 802.1x support, you need to enable a Wireless service, even though you may well be using it on a wired connection. Intuitive, eh?

When AirPcap was first released, only WEP decryption was supported. However, with the release of Wireshark 0.99.5 it is possible to decrypt WPA packets with the AirPcap adapter in Windows. Here’s how:

1. Install Wireshark 0.99.5 or above
2. Run Wireshark
3. Go: View > Wireless Toolbar
4. Click on “Decryption Keys…”
5. Add a new decryption key. In my instance, because I know the Passphrase, I used WPA-PWD. If you’re doing penetration testing and, you have a 64byte string from something like AirCrack, you should use WPA-PSK.
   
6. Capture away. In the screenshots below, I’ve filtered my own Wi-Fi card to cut down on the volume of ‘junk’ and demonstrate that it is, in fact, decrypting the packets on the WLAN.
   

For a lot more information on getting this set up, check out the AirPcap Userguide.

Did this help you at all? Any questions? Feel free to leave me a comment below!

Admittedly it’s a long time since I ran a reinstall, but from memory, it must be done with a Windows 2000 client: XP just plain refused to work.

Dell’s article should cover everything you need to know.

I solved the problem by uninstalling the NIC driver and letting it re-install after a reboot, but I’d love to know what may have caused the issue!