A typical router acts as a DHCP server, using the Dynamic Host Configuration Protocol to assign IP addresses automatically to each device that connects to its network. Although this enables you to connect a device to your network without manually assigning it an IP address, it also allows other people in range of your network to connect to it without authorization. To determine if someone outside your home is accessing your network resources, open your router’s DHCP client list.
Open a new browser window, then enter your router's IP address in the address bar. Refer to your browser's user manual to find the device's IP address.
Type your router's login information in the Username and Password fields to open the Web Setup page. Check the router's documentation for the default login information.
Locate the list of devices that are connected to your network. Depending on the terminology of your router's manufacturer, you can find the list under "DHCP Client List" or "DHCP Client Table." For example, if you have a Linksys router, select the "Status" tab. Click the "Local Network" sub-tab, then click the "DHCP Client Table" button to display the list of connected devices. If you have a Belkin router, click "DHCP Client List" under LAN Setup to view the list.
Review the list to determine if there are any unauthorized devices connected to your network. Compare the information for each device on the list to the known devices on your network. For example, compare the IP address of each device on your network to each IP address on the DHCP list. If an IP address, MAC address or name does not match, there are unauthorized devices connecting to your network.
Hide your network's SSID to stop broadcasting your network's name to anyone within range of its signal.
Activate your router's security protocols -- such as WPA security -- to prevent unauthorized devices from accessing your network.
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