Have I met you before?: using cross-media relations to reduce SPIT

Most legitimate calls are from persons or organizations with strong social ties such as friends. Some legitimate calls, however, are from those with weak social ties such as a restaurant the callee booked a table on-line. Since a callee's contact list usually contains only the addresses of persons or organizations with strong social ties, filtering out unsolicited calls using the contact list is prone to false positives. To reduce these false positives, we first analyzed call logs and identified that legitimate calls are initiated from persons or organizations with weak social ties through transactions over the web or email exchanges. This paper proposes two approaches to label incoming calls by using cross-media relations to prior contact. One approach is that a potential caller offers the callee his contact addresses which might be used in future calls. Another is that a callee provides a potential caller with weakly-secret information. In order to be identified as someone the callee contacted before through other means, the caller can convey the information in future calls. The latter approach enables a callee to label incoming calls even without caller identifiers. Reducing false positives during filtering using our proposed approaches will contribute to the reduction in SPIT (SPam over Internet Telephony).