You might look for logs such as LAN users, connection or status log, or connected MAC addresses. And you can also use a tool to check the IP/MAC on your wireless network IP range.

Verify the MAC addresses

To find out who is on your network, you have to make a list of all the devices that are meant to be connected. Find out their MAC adresses and their IP addresses if they are static.

To find out the MAC and IP address on Windows OS, click the Start menu and choose Run. Type cmd and click OK. In the screen that opens, type ipconfig/all and hit Enter. The MAC address will be shown as the physical address.

Once you know the MAC addresses of each of the computers on your wireless network, you will recognise any addresses that don’t belong under the window that shows the MAC addresses of current clients.

Check the IP addresses

Similarly you can see how many IP addresses have been dipped out by the DHCP server. If you check the IP of each of your computers, you can see if other IP addresses have been used in your wireless network.

To find out your IP address on Windows OS : Click Run ? type in cmd ? type ipconfig/all ? which will display the IP address for that computer.

Use a software to scan for IP/MAC

Zamzom Wireless Network Tool (google it for download) is a free tool that can do a quick scan for you. Just load it up, hit Fast Scan and it will show you the IP and MAC addresses of every computer that is connected to your WAN. You can also perform a deep scan, but a fast scan will be enough for most users.

Dealing with intruders

If you find someone using your wireless router, they may well not be doing so nastily or intentionally. Sometimes people can’t tell which is their own connection and they may honestly believe that they are using their wireless router. In this case, the best thing that you can do is to secure your own wireless network.