Illegal Access Point called as Rogue Access Point (RAP) is an access point that has been installed on a secure network without explicit authorization from a system administrator Wireless Networks has big security threat called Rough access points. If care is not taken and if this network threats are not detected and mitigated on time, this will result into the serious network damage and data loss. Every organization should give priority for Finding and avoiding rogue wireless access points. For detection of unauthorized AP', we have use clock skew as a parameter of a wireless access point (AP). For detecting Rogue access point using clock skews method in wireless LAN network overcomes the limitations of existing solutions. For calculating clock skew of AP, we have use IEEE 802.11 Time Synchronization Function (TSF) time stamps sent out in the beacon/probe response frames. We mainly focus on implementation of least-square fit method for this purpose though we have explain both approach for detecting clock skew From this studies we came to known that use of clock skews appears to be an effective and robust method for detecting fake AP's in wireless local area networks.