Trust-based SPIT detection by using call duration and social reliability

Spam over Internet Telephony (SPIT) refers to a prerecorded advertising call using the Voice over Internet Protocol (VoIP) as a medium. It is expected to be a serious problem in the near future because of the rapidly growing number of VoIP users and the cost-effectiveness for spammers. The real-time nature of a call makes it difficult to detect SPIT. This paper describes a trust-based SPIT detection model that is effective and should be acceptable to call participants because it does not require any interaction from the users. To discriminate legitimate callers from spammers, a trust value is computed from the duration of a call and its direction between users. We propose a trust inference mechanism to calculate a trust value for an unknown caller by using the Dempster-Shafer theory. The social reliability based on past behaviors of a caller is also considered before forwarding a call to a callee. We evaluate the proposed system on different types of network datasets. The experimental results show that our approach is effective in identifying SPIT with a low rate of false positives. The difference of network distribution and the number of spammers do not affect the detection accuracy.