100% credit goes to Bill Mullins for sharing this information. (BillMullins.wordpress.com).
Softperfect has some of the best freeware for Windows. With Netscan you can see devices on your network and find information about the devices. Now with their software “WiFi Guard”, you can use a device on your network and find the devices that are attached to it.
While you should take precautions to secure your wireless network, is someone accessing your network without your knowledge?
Installation is fast and easy. Simply follow the wizard and make sure you run the software at startup.
Once you install the software, select the adapter and scan your network. Next double click on known devices and select “I know this device.” Let the software run and periodically scan your network. If you find a device connecting to it, locate the device and remove it from the network or take action to prevent unknown devices from connecting.
The software is designed to run on Apple, Windows or Linux.
Note: The above pic is from a lab environment and the addresses and macs do not represent real machines or a production environment.