Wifi Network Tracing by Martin Sauter

Martin Sauter started to post a milti-part tutorial on wireless network tracing. Part 1 is about the setup - Windows, Wireshark, a Linksys WRT54, OpenWRT and Kismet.

Taking traces in a Wireless LAN can be quite a tricky thing if you are using Windows. Except for a few expensive programs which can do the job, other free tools like Wireshark can only trace what the network driver forwards to the operating system. Unfortunately, Windows network drivers only forward pseudo Ethernet frames to the OS and hide all the nitty gritty Wireless LAN details. An alternative to tracing a Wireless LAN with your PC is to let an off the shelf Wireless LAN access point record all packets and save them to a file which can then be analyzed on the PC. Cost of the solution: 60 euros and a bit of time to set it up.

The Wifi tracing environment consists of the following components:

• A PC or notebook running Windows with an Ethernet port.


• A Linksys WRT54G or WRT54GL wifi router (picture above, for details see below). The WRT54G sells for around 50-60 euros on eBay. Several hardware versions exist, not all of them are suitable. For details, see the next blog entry.


• OpenWRT, a free Linux operating system for the wifi router (open source)


• X-WRT, a better web interface for OpenWRT (open source)


• Kismet for OpenWRT (open source)


• CIFS driver for OpenWRT to be able to mount a directory of your windows computer on the router for file export (open source)


• Wireshark for Windows (open source)


• Putty for Windows, a free telnet/ssh shell for Windows

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As seen at Martin's Mobile Technology Page