WiFi Inspector is a simple application that we can install without too many complications, which will allow us, in just one step, to know which devices are connected to our WiFi network, so that we can locate those that are not ours. Once the application is installed, we just have to run it, and it will tell us what is the name of the WiFi connection to which we are connected, as well as other relevant data, such as the IP address, the MAC address, the gateway , the netmask, the connection speed, the DHCP server, and the DNS addresses. This data can be useful to better understand the connection.
However, what we want to know is which devices are connected that are not ours, and for that we just have to press the Search Intruders button. In reality, it will not tell us all who are intruders, but all the devices that make up the wireless network. Among them, there is the gateway, which is our own router, which will be the only one that it will recognize as ours, apart from our own smartphone. In addition to these, many more will appear to us who recognize them as unknown. These unknown devices are also ours, such as the computer, the game console, the tablet or other smartphones. With the IP address, as well as the manufacturer, we can recognize what they are, and even add them as our own devices. If we find one that is not our own, or that is not one of ours, then we already know that we have someone connected to our wireless network. On the other hand, when we do the search again, as we already have our own devices saved, it will be worth noting if there is one that is unknown, since all of our previously added ones will be recognized as known devices.
WiFi Inspector is a free application that is very easy to use and is available at Google play.