I got the following inquiry from a client today, “ Can you tell if anyone is using your wireless router who does not live in your house?”
The answer is – yes you can, but it takes a little detective work. First you need to log on to your wireless router. Usually you can do this by opening a browser window and entering the router IP address. This is commonly http://192.168.1.1. Then you will need the user ID and password, and this is usually found in the router documentation.
Your Wireless Router will be assigning the IP address using a process called DHCP. On my Linksys router, this information can be found on the Status Tab under Local Network. Click on the DHCP Clients Table (below). On other manufacturers you will just need to search for the DHCP assignment list. (Click on the image to enlarge it)
Here is where the detective work comes in: You need to get the MAC addresses of the computers in your house, both wired and wireless, and then compare them to the addresses on the list. Or if you have 2 computers in your house and 3 or 4 computers on your list, you can determine if there are more than should be there simply by counting.
To get the MAC address and assigned IP address, open a Command Prompt (START, Run, CMD or All Programs, Accessories, Command Prompt) and type in ipconfig /all leaving a single space between ipconfig and /all.
Every computer ( actually, every network card) has a hard coded address called a MAC address. It is a hexadecimal address and usually looks like this: