SoK: Fraud in Telephony Networks

Abstract

Telephone networks first appeared more than a hundred years ago, long beforetransistors were invented. They, therefore, form the oldest large scale networkthat has grown to touch over 7 billion people. Telephony is now merging manycomplex technologies and because numerous services enabled by these technologiescan be monetized, telephony attracts a lot of fraud. In 2015, a telecom fraudassociation study estimated that the loss of revenue due to global telecom fraudwas worth 38 billion US dollars per year. Because of the convergence oftelephony with the Internet, fraud in telephony networks can also have anegative impact on security of online services. However, there is littleacademic work on this topic, in part because of the complexity of such networksand their closed nature. This paper aims to systematically explorefraud in telephony networks. Our taxonomy differentiates the root causes, thevulnerabilities, the exploitation techniques, the fraud types and finally theway fraud benefits fraudsters. We present an overview of eachof these and use CAller NAMe (CNAM) revenue share fraud as aconcrete example to illustrate how our taxonomy helps in better understandingthis fraud and to mitigate it.