Using E-Mail SPAM DNS Blacklists for Qualifying the SPAM-over-Internet-Telephony Probability of a SIP Call

SPIT is an upcoming threat for receiving unsolicited messages in Voice over IP systems. We assume, that future SPIT will be sent through the same infrastructure as SPAM today, namely through a network of compromised hosts. Therefore spammers will see SPIT as an additional business case. In this paper we show a viable way to increase the hit rate of a SPIT detection system. Our proposal is to query e-mail SPAM blacklists for IP addresses which are sent with SIP/SDP messages. We enabled a well-established e-mail filter application to handle information out of these messages. We also present the performance of such a solution with respect to call setup delays and success rates.