Studying for CWAP, I embarked on a mission to capture 802.11 management frames using my Windows laptop. For those with MacBooks that do this natively, read no further, just keep on perfecting that smug look of disdain with a slight hint of pity for the rest of us Microsoft peasants.
For those whose laptops aren’t fruit branded, but you still want to capture 802.11 frames in promiscuous mode, this is the post for you. Especially if you can’t quite justify the cost an AirPcap adapter for study purposes.
While researching alternatives to pricey AirPcap adapters, I came across this Acrylic WiFi Professional post on their option for an NDIS driver. This driver allows you to capture in promiscuous mode, so you can capture all that management frame goodness, but without the AirPcap adapter. I checked out the supported USB wireless options, ordered one off the list from Amazon (I picked the NETGEAR A6200), and downloaded a free trial of Acrylic WiFi Pro to get started.
The installation of Acrylic Pro is straightforward, as is turning on Monitor Mode when you know where to look. By default, Monitor Mode is turned off and the NDIS driver is not installed. Just click the menu in the right corner, and select Change to get to the Monitor Mode settings.
Select Monitor Mode On and select Install the NDIS driver. You’ll get a warning message that you might crash your system and you’ll need to acknowledge that you are completely okay with this*.
Once the driver is installed you can swap over to the Packet Viewer using the icon in the top tool bar or by clicking Packet Viewer from the menu. You will also see that you are in Monitor Mode and can select to change out of Monitor Mode if so desired.
While all of this is really super cool, I was extremely interested in capturing these frames inside of my most familiar tool of packet sniffing choice, Wireshark.
Unfortunately, I didn’t see the NDIS driver as an available capture interface when I launched the Wireshark application. This post by Acrylic reminded me why. I needed to launch Wireshark with Run As Administrator, even though I am a local administrator on the laptop**. Once I did this, I could select the Acrylic NDIS NETGEAR A6200 WiFi Adapter and start capturing wireless management frames.
I could also select the Wireless Toolbar in Wireshark and see that the NDIS driver emulating an AirPcap adapter.
Unfortunately, I still had one tiny problem at this point. Every time I launched the Wireshark application, my built-in wireless card immediately quit passing all traffic. Not exactly ideal for productivity.
Easy fix, though, if you encounter this issue. Head over to the settings for the Network Adapter, uncheck the Tarlogic NDIS Monitor Driver for the built-in adapter, and the problem is solved.
I would be remiss not to point out that there are limitations to this NDIS driver. For instance, there is no support for 40 or 80 MHz channels at this time. But for my CWAP study purposes, this is working quite well and saves me a bit of cash. Also, Ben Miller did a great write up on this very same subject, which, of course, I found just AFTER I went through this process and drafted this post. The universe has quite the sense of humor like that.
*Do this at your own risk, please don’t blame me for your system crash, there’s a good chance I’ll just point and laugh…
**If you need to know how to set a program to always run as administrator in Windows 10, look here.