On Spam over Internet Telephony (SPIT) Prevention

Spam over IP telephony (SPIT) is expected to become a serious problem in the near future. One of the main requirements for a SPIT prevention system is to avoid the involvement of the callee in the SPIT detection process, because this implies disturbing the callee each time an unclassified potential SPIT call arrives. Further requirements include adaptability to different deployment scenarios and flexibility to quickly react to new kinds of SPIT that bypass existing prevention systems. This article analyzes the requirements for SPIT prevention, provides a systematic classification of currently known SPIT prevention methods, and introduces a reference model for SPIT prevention systems. As an instance of the reference model, we designed and implemented an advanced SPIT prevention system, composed of methods that avoid unnecessary callee interaction and adaptive in order to be customized for different scenarios.