3D physical localization of voice phishing SIMBOX on cellular networks

Abstract

The total financial loss due to voice phishing within Korea has risen to over USD 620 million in 2020. Most of the crimes involve a SIMBOX, serving as a VoIP (Voice over IP) gateway, that can hide the origin of the call. Voice phishers located outside of a country utilize the SIMBOX to make a fraudulent local mobile call. To address voice phishing crime, various methods have been proposed and utilized, most of which are passive. One active defense mechanism currently be used is to physically localize and confiscate the SIMBOX. At present, to confiscate the SIMBOX, the police obtain information of the cellular base station where the SIMBOX is located with the cooperation of the carriers. As most of the existing SIMBOXes support 3G calls, they then monitor the existence of the uplink 3G communication signal within the base station using radio equipment. Finally, using directional antennas, they can localize the SIMBOX by following the direction of the signal. This mechanism, however, would not work against SIMBOX supporting VoLTE (Voice over LTE), because most of the UE (User Equipment) currently utilize VoLTE. More precisely, it is impossible to distinguish whether the uplink signal is generated by the SIMBOX used for voice phishing or normal UE in the current cellular network. To solve this problem, we propose two approaches for the 3D physical localization of voice phishing SIMBOX on LTE cellular networks. First, we develop a technique that can distinguish the uplink signal of the SIMBOX from that of the normal UE. Second, we propose a mechanism where the base station directly allocates a specific uplink frequency to fingerprint the signal from the SIMBOX. Using directional antennas, we can localize the SIMBOX as in 3G cases.