Networking/Computing Tips/Tricks

As many of my clients and students know, I have agreat solution for those who want to capture WLAN control and management frames using a Windows system without paying anyone any money for expensive interfaces or software.  THIS IS ONLY ABOUT SEEING THE Wi-Fi CONTROL AND MANAGEMENT – for example if you wanted to capture TCP traffic between your system and another system, to Wi-Fi this is considered Data traffic.  Wireshark allows capture of normal Wi-Fi data traffic with your Wi-Fi NIC in managed mode – however it just looks like Ethernet traffic (even though it isn't).  You can stop reading here.  

If, on the other hand, you want to put the NIC into monitor mode to listen to control and management frames, like beacons, Clear to Send, Request to Send, Association, Disassociations, etc. AND you have Microsoft Windows, then this article is for you.

The problem comes down to our friends at Microsoft.  Windows, by definition, does not allow users to put their interface into "Monitor Mode".  So if you use a great packet dissector like Wireshark, you can't really see the WLAN packets.  You have 4 options:

  1. Buy the Riverbed Airpcap tool which is ridiculously expensive ($700 plus) but works perfectly.
  2. Use Acrylic WiFi solutions to essentially install drivers that may or may not work.  I have not had any success with this, but some say it works for them.
  3. Run Linux as a dual boot, USB boot, or VM.  There are some complications to the VM part.  I have written separate articles on these VM options here.
  4. Want to stay with Windows only?  There are two possibilities:
    1. Use my solution below which is free and works 100% of the time
    2. Use the Npcap driver that now is a preferred option at install of Wireshark and used to come with nmap.  If you use the npcap driver and can get it to work, it is better than Winpcap because it has been updated and Winpcap is no longer being updated.  The problem is that for many - upgrading from Winpcap to Npcap has been troublesome and after installing Npcap they cannot see any interfaces in Wireshark.  The folks at Nmap are working on this. I have had mixed success with it.  Npcap requires that you get rid of Winpcap and vice versa.  If Npcap works, then you can run Wiresahrk in "Administrator Mode" and actually put the Wireless interface into monitor mode from the Wireshark Capture> Options screen.  If this could be made stable, it would be a great solution. If you can get Npcap working, you do not need to read any further.

Here is how you do it:

First go to this link and download/install Microsoft Network Monitor v3.4.  This is ancient software (actually in Microsoft's archives) but works on all older and newer versions of windows (I am using Windows 10 and it is perfect).  That said, you will see in the comments that some folks find they cannot get their newer generation USB Wi-FI NICs into monitor mode.  If that is you, then option 3 above is your best path.  Let’s continue:

Run the installation process.  It takes about 5 minutes.

You will need to reboot.   You will also need to have Administrator privileges.

Once rebooted - run the program.  It will look something like this:

msmonitor1

You will note that all the interfaces (bottom left) are selected by default.  To capture Wi-Fi packets, deselect all except the Wi-Fi interface of your computer:

msmonitor2

Next, select 'New Capture':

msmonitor3

The screen will change as shown:

msmonitor4

You will see the Wi-Fi interface selected, but you need to adjust the properties (the first time).  So select the interface so it is highlighted, then click the properties button:

msmonitor5

You will get a Network Interface Configuration pop-up, and you will select the Scanning Options button:

msmonitor6

When you do this you may get a permissions warning...of course, say yes to this.

You will then be presented with the Wi-Fi Scanning Options dialogue, and it is in this next screen that you must select Switch to Monitor Mode:

msmonitor7

The bottom list of 802.11 options will now not be greyed out:

msmonitor8

I suggest you leave them all selected.  Now the next step is tricky.  Even though the "Close and Return to Local Mode" button is highlighted, you will want to click on Apply.  Then close the dialogue with the "X" on top right.

We are now ready to capture!!

Click the "Start" button on the top menu:

msmonitor9

And *POOF* you are capturing WLAN packets!!!

msmonitor10

When you are ready to stop, click on the Stop button, and save the file (Save As something like test.cap to your desktop).

Now you can open that .cap file in Wireshark:

msmonitor11

There are a couple of differences you might notice.

First instead of Radiotap headers, you will see Netmon headers.  They are almost identical, and you can still retrieve important WLAN information like speeds, signal, and noise levels.

Also, Wireshark may report Malformed packet errors, that can be ignored.

How cool is that!

Sorry Riverbed, and sorry to all those who say it can't be done without $$$.

Comments are welcomed!

[Note:  If you cannot get this to work, I suggest you read this article as well.]

 

 

 

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