You can SPIT, but you can´t hide: Spammer identification in telephony networks

Spam over Internet Telephony (SPIT) is a new form of spam delivered using the phone network. With the low cost of Internet telephony, SPIT has become an attractive alternative for spammers to carry out unsolicited marketing and phishing. SPIT is more intrusive than email spam as it demands immediate recipient attention. In this paper, we study characteristics of communications in a phone network with the objective of identifying “SPITters”. We collect and analyze the data from one of the largest phone providers in North America. First, we propose a new technique, Loose Tie Detection (LTD), to identify outliers based on social ties. Second, we introduce Enhanced Progressive Multi Grey-Leveling (EPMG), which identifies outliers based on call density and reciprocity. Finally, we propose SymRank, an adaptation of the PageRank algorithm that computes the reputation of subscribers based on both incoming and outgoing calls.We evaluate the three techniques and find that they compute an overlapping set of outliers. Our experiments reveal that LTD and SymRank - although seemingly independent approaches - closely match with regard to outliers, thus showing that our techniques are effective in identifying SPITters.