A group of vendors and technicians has quietly been demonstrating secure, multivendor VOIP connections. The InteropLabs demo focuses on two major areas of security: protecting the SIP gateway from attack and supporting remote users connecting via a VPN. The demo shows that it is possible to support VOIP within the closed confines of a single enterprise. Experts disagree on the immediate need for VOIP encryption, but Nortel acknowledges encrypting VOIP eventually will be necessary. The decision on whether to encrypt VOIP depends on how the VOIP travels over the network, the enterprise’s need for security.”]
Source: https://www.darkreading.com/analytics/yes-virginia-voip-can-be-secure