A method and system for identifying short message service (SMS) spammers identifies senders as spammers by determining that the senders are sending SMS messages to devices included in a grey phone space. Devices in the grey phone space are identified using various methods including an analysis of call detail records. A grey ratio for a sender is determined as a ratio of messages sent to grey phone numbers by the sender to messages sent to all phone numbers by the sender. A sender is identified based on a difference between the grey ratio for the sender and a second grey ratio being above a threshold.