Security is often cited as one of the primary reasons organisations have not deployed VoIP. Network managers need to cut through the hype and deploy the right security to maximise the reliability of the voice network and have a successful rollout. The shift to VoIP changes many things. With voice the old TDM way, the PBX was a stand alone closed system with phones directly connected into them. Its simplicity was also its security. Of course, the problem with this model is that sharing applications was difficult; moves, adds and changes were expensive and there was no integration with the data network. A VoIP system looks a lot like any other networked application. There's a call server, mail server and other applications running on commercially available hardware with IP endpoints that communicate with it. These servers and end points communicate via an IP-over -Ethernet network connected with switches and routers. Since a VoIP system parallels other IP applications, the threats to it are similar and require an understanding of how the VoIP components are impacted.