Log in to the router management interface through the IP address. Due to different wireless routers, the URL /IP address of the login settings page is also different. So you need to find out what the address of your wireless router is first; You can see it on the nameplate at the bottom of the router, as shown in the figure below.
Open the browser in the computer, enter the router setting URL in the address bar of the browser, open the login interface, and enter the password of the administrator account to log in to the settings page.
Click the "MAC address filtering" option to see how many devices are connected to this wireless router to surf the Internet. As shown in the figure below, three devices are shown. You can compare the total number of devices here with the number of computers and mobile phones in your home. If the number is the same, it means that your wifi has not been accessed by others.