The VoIP Security Threat Taxonomy

This VoIP Security Threat Taxonomy is meant to define
the many potential security threats to VoIP deployments, services, and
end users. Part of the challenge of devising effective VoIP security
protections requires first identifying these threats in the first
place. The overall goal of this project is to help ground VoIP security
awareness in the industry, press, and general public.

The chapters header are Social Threats, Eavesdropping, Call Pattern
Tracking, Traffic Capture, Interception and Modification, Service
Abuse, Intentional Interruption of Service (DOS), and Other
Interuptions of Service.  This is a great reference document that
should put everyone on the level when discussion VOIP threats and
risk.  It authored by VOIPSA (the same guys who analyzed the security of Skype), and was posted on Astalavista (PDF).