Why VOIP Needs Encryption
With the increasing popularity of Voice Over IP (VoIP), a lot of people are starting to question themselves about how secure the technology really is. Eavesdropping on an unencrypted VOIP conversation is as easy as breaking a network password; If you have the right tools, anyone could do it. If you guys are interested about looking at such a tool, Cain&Abel will probably satisfy your curiosity. I reviewed the password cracking functionalities of the application right here, but unfortunately, the VoIP sniffing module isn't covered in the review.
Bruce Schneier, CTO of Counterpane Internet Security, published a good article exposing some of the security problems related to Voice over IP. If you plan to switch your traditional phone line to a VoIP one, I would suggest that you read this article today to learn about what you're getting yourself into.