A WPA key finder is a software tool or mobile app that recovers WPA network passwords in one of two ways. Some WPA key finders use a list of default router passwords to attempt to connect to a network. Other WPA key finders scan the host computer for stored passwords and then attempt to use these recovered passwords to connect to the network.
The first type of WPA key finder operates on the assumption that many people never change their default router passwords and always leave them set to the factory defaults. By identifying a router model and then scanning a database of factory default router keys, this type of WPA key finder can connect a device to the network, provided the router password has never been reset. If a user ever defined a personal password for a router, these types of key finders are useless.
The other type of WPA key finder takes advantage of the fact that most computers and mobile devices store the passwords to every network they have ever connected to, as this prevents users from having to enter the passwords every single time they connect. These WPA key finders can be very useful if a user forgets a password, but only if the password has not been changed since the last time the device connected to the network.
Neither type of WPA key finder can recover a password for a network to which the host device has never connected, nor can the key finders recover passwords for networks where an administrator changes a password.