I see that Syngress has just released a new title focused on VoIP security. Practical VoIP Security was written by a team that includes Thomas Porter, Larry Chaffin, Andy Zmolek, Choon Shim, and Jan Kanclirz, Jr. It sounds like a good read that covers a lot of ground and is based on the real-world experiences of the authors (something that can make or break a book in my opinion, I like my books with a healthy dose of practical information which is usually best gleaned from people actually working in the field). Another one to add to my must-read pile. From the press release:
This book was written for the thousands of IT professionals–from CIOs to circuit-switched telecom engineers–who are now responsible for deploying and maintaining secure VoIP networks. The impact of PSTN, SIP, H.323, firewalls, NAT, encryption, and the regulatory environment on your VoIP network is thoroughly explained. Coverage includes evaluation, design, integration, and management of VoIP networking components, including IP telephones, gateways, gatekeepers, registration servers, media servers, and proxy servers. Throughout the book, the authors rely on their extensive real-world experience to provide readers with practical applications and solutions.