Voice over Internet Protocol is the real-time transmission of voice signals using the Internet Protocol over the public Internet or a private data network. VoIP converts voice signal from the telephone into digital signal that can travel over the internet. Nowadays, even small and medium businesses are interested in implementing VoIP. However, VoIP is prone to the external threats such as vishing, spoofing, phreaking, VoIP spam or unwanted calls. The researchers proposed to
implement a Web-based caller ID blocker application for asterisk server using Global System for Mobile gateway. This web based application aims to extend the capabilities of asterisk server for blocking any suspicious calls within and outside the LAN. The administrators have a full authority access to the web based caller ID blocker application. The administrator has an authority to block any incoming calls. This will help the administrator to reduce possible attacks that can harm the company who are using VoIP technology. This research web-based caller ID blocker application for asterisk server using GSM gateway aims to reduce the VoIP attacks that can harm entirely the network and the company. Furthermore, it will also identify the caller IDs that will be blocked by the administrator who has the full authority in blocking and unblocking inbound and outbound calls.