Caller ID spoofing), allowing caller to represent himself as relative, colleague, or part of the family, in order to extract information, money or benefits from the target. Secure SIP Port FreePBX has inbuilt firewall, you can use that to secure SIP port. See also Comparison of VoIP software INVITE of Death List of VoIP companies Mobile communications over IP - Mobile VoIP Voice over WLAN - VoIP over a WiFi network References Internet security