In this paper, the authors have discussed about attacks performed on false base station. In GSM network environment all the communication has restricted between mobile station and base station which call has been transferred. This GSM network has few draw back which are discussed in this paper. This is also about how call has been forwarded to mobile switching center and base station. GSM network contains about different types of encryption and decryption mechanism between call transfers. The attack makes intruders to impersonate GSM base station and make it impersonate user to get connect within base station.