1. A method for increasing security of plaintext authentication in a wireless local area network (WLAN), the method comprising steps of: establishing a basic server set in the WLAN; establishing a blank learning table for saving identities of the faked users; generating identities to the faked users; performing a faked extensible authentication protocol process according to the generated identities; determining whether the learning table should be updated; and updating the learning table if the learning table should be updated.