After collecting unencrypted plain text, cipher text exchange between MS and BTS and the corresponding frame number it is easy for an eavesdropper to retrieve a BLOCK associated with RAND as describe above. It is genuine that whenever the user sends SMS it is encrypted with corresponding cipher key KC. However in this case an eavesdropper is able to decrypt the message sent over air interface with the help of parameter that he had collected . Now by then an attacker can modify the message. Again the system does not offer any provision for MAC value or hash function for user in order to be sure that the message is not tempered in the middle by any intruder. Hence alteration or modification of message is still the existing threat for system.