In this paper, we conduct a comprehensive study of SMS spam in a large cellular network in the US. Using one year of user reported spam messages to the network carrier, we devise text clustering techniques to group associated spam messages in order to identify SMS spam campaigns and spam activities. Our analysis shows that spam campaigns can last for months and have a wide impact on the cellular network. Combining with SMS network records collected during the same time, we find that spam numbers within the same activity often exhibit strong similarity in terms of their sending patterns, tenure and geolocations. Our analysis sheds light on the intentions and strategies of SMS spammers and provides unique insights in developing better method for detecting SMS spam.

With widespread adoption and growing sophistication of mobile devices, fraudsters have turned their attention from landlines and wired networks to cellular networks. While security threats to wireless data channels and applications have attracted the most attention, voice-related fraud activities also represent a serious threat to mobile users. In particular, we have seen increasing numbers of incidents where fraudsters deploy malicious apps, e.g., disguised as gaming apps to entice users to download; when invoked, these apps automatically - and without users' knowledge - dial certain (international) phone numbers which charge exorbitantly high fees. Fraudsters also frequently utilize social engineering (e.g., SMS or email spam, Facebook postings) to trick users into dialing these exorbitant fee-charging numbers.