I. Introduction
Caller ID is a telephone service that allows a subscriber to identify the telephone number of a caller before answering the call [1] therefore allowing the receiving party to make assumptions regarding the identity of the calling party even before the call starts. This in turn creates a trust relationship between the call initiator (caller) and the call recipient (callee) prior to the first vocal interaction between them. Unfortunately, unlike the Domain Name System (DNS) or other similar mechanisms, there is no regulating authority for the Caller ID. Besides that, the service has not been designed with regards towards possible attacks and is therefore widely open to attacks like spoofing. In such cases, the caller simply pretends to be somebody else, by deliberately changing his/her Caller ID. As Volodymyr L. Buriachok et al. state in their work, caller ID spoofing is uncomplicated to launch, nevertheless difficult to detect and defend from, even in 4G LTE networks [2].