A mobile telecommunication network monitors short messages and multimedia messages sent to non-existent mobile subscribers and selectively treats such messages as if sent to an existent recipient. The network then provides the sender with ordinary signaling related to successful message delivery so as to form traps to attract and detect messages such as spam messages. Spam messages are detectable as statistically significant presence of identical or sufficiently similar messages in a sufficiently large subset of unused subscriber numbers being assigned as traps for spam messages. The treatment of messages addressed to numbers assigned to trap use can further model normal usage of mobile subscriptions so as to inhibit simple determination of subscriber numbers that are used for trapping spam messages.