A VoIP SPAM reduction framework

SPAM over Internet Telephony (SPIT) has become a critical problem especially because VoIP systems are widely deployed. Identifying VoIP SPAM is more problematic compared with e-mail SPAM mainly because of the different nature of each of them. In this paper, a new approach is introduced to reduce VoIP SPAM by ranking VoIP callers based on a set of parameters. These parameters include the caller´s reputation, the feedbacks (if any) collected from the callee, and whether the callee responds or ignores the call. Additionally, a set of dummy directory numbers is introduced in the callee´s domain. These numbers work as traps for certain kinds of VoIP spammers who try to guess the directory numbers in the victim´s domain or overwhelm this domain by dialing random directory numbers. The VoIP caller is scored based on an identification process that uses these parameters and, hence, the caller´s reputation is adjusted. This score is communicated to the callee for each incoming call and the final decision to accept/reject the call is taken by the callee himself. Additionally, this score can be utilized as an acceptance/rejection probability to automatically accept//reject the incoming call. A theoretical analysis is carried out for the proposed framework. Furthermore, the effectiveness of the proposed framework in dealing with VoIP SPAM is verified by simulation studies.