In this paper, the work involves setting up a secure VoIP solution. At first, we presented some attacks scenarios affecting confidentiality, authenticity and integrity in the VoIP network. In the second part, we focused on VOIP security themes, so our work has focused on areas where enhancing VoIP security is essential. The convergence towards everything of IP is now a reality. The efforts made by infrastructure providers, whether fixed, mobile, and cabled or wireless. This is also evident in operators who now only design the services they offer in the context of everything IP. But with the increasing use of Voice over IP (VoIP) technology, services and protocols are becoming increasingly vulnerable. In this context work several organizations that promote the research and development of network security, warn users of the attacks risks that may affect the communications confidentiality. This work proposed to explore the security vulnerabilities associated with VoIP networks and to present some solutions to avoid and minimize these threats.