Yeah I know, who hasn’t heard of this tool.  I searched our tools list here and didn’t see it posted and considering it is one of the most important wifi discovery tools out there, I thought it was worthy of its own post. Also, if someone is absolutely new to security, they better become familiar with it quickly.
  The 2 most powerful aspects of Kismet is that is can discover cloaked access points (netstumbler cant) and will show you the mac address of anyone connected to the wifi network even if you are on the outside of that network.  This one feature of exposing the Mac address should quickly educate people why security through mac filtering is such a waste of time. While most home APs will not allow two identical IP addresses, they allow multiple identical mac address to connect at the same time! Even if the AP didn’t, it would easy be enough to wait until the accepted mac id disconnected and then you could jump on spoofing the allowed address.  If the average home wireless AP would not spill out the connected mac address for all to see, this alone would make mac filtering so much more powerful. Infact, it would make it a better security than wep or wpa.

http://www.kismetwireless.net/

I also consider Kismet a must have assessment and penetration tool.  However, sometimes you will not want to capture any packets but still find cloaked SSIDs.  You should look into a tool called wellenreiter by Max Moser, Steffen Kewitz, and .Martin J. Muench at http://www.remote-exploit.org/codes_wellenreiter.html.

Just getting my feet wet, but is there a windows xp version of Kismet that doesn't require a separate aircap type adapter but can use standard laptop wireless card such as Dell's 1390 WLNA mini card?

Ken