The Voice over IP Security Alliance (VOIPSA), a non-profit that "aims to fill the void of VoIP Sercurity related resources" is working on a open VoIP security threat taxonomy project.

VOIPSA is seeking help from individuals and organizations interested in furthering the goal of security through a collaborative, consensus process.  Some of the issues they’re interested in working on include social threats (such as misrepresentation or theft of service), eavsdropping, interception and modification, and intentional/unintentional interruption of service.

If you’re interested, you can check out VOIPSA’s Taxonomy Wiki or Homepage.

This sounds like a good way to go about documenting, and then later addressing, the security threats facing VoIP and child technologies that come out of it. Since VoIP is already mission critical for so many businesses and even emergency relief organizations now (and of course this is only increasing), working on these security issues is critical.