The VoIP system is build on the IP network, so it is affected by the IP network security problem. It has many security problems because of the security mechanism of VoIP system and other external factors. These effects relate to the following three aspects: confidentiality, integrity and availability. This paper makes a detailed analysis discussed several security potential threats by dividing it into several categories like social, eavesdropping, service abuse, etc. and finally shows how this threats are harmful to VoIP. Keywords-VoIP; Security threat
