A method and apparatus for identifying an unwanted short message service (SMS) message from SMS messages received by a cellular mobile communication system, which comprises at least a history database (HB) for storing a set (H) of the messages received by the cellular mobile communication system. The method includes the steps of: measuring a difference in an information content between a SMS message (m) received by the cellular mobile communication system and the set (H) of messages stored in the history database (HB), and marking the SMS message (m) as being an unwanted SMS message if the difference that is measured is less than or equal to a predefined threshold value.