There’s a good discussion going on right now (September 2014) in the VoiceOps mailing list about how you can mitigate SIP threats by configuring the policies and settings on your session border controller (SBC). It started out with a detailed question from Robert Nystrom asking about how to configure an Acme Packet SBC in the most secure manner and asking about how best to configure access control lists (ACLs). Several answers can be seen in the VoiceOps archive from folks such as Ryan Delgrosso, Mark Lindsey, Jim Gast and Patrick McNeil, offering commentary and suggestions about how best to proceed.
If you are not already subscribed, the VoiceOps mailing list is a great resource. As stated on the subscription page:
This list is for discussions related to managing voice networks, both traditional and IP.
The VOIP Operators’ Group (VOG) charter is to facilitate the creation, maintenance, and operations of Voice over Internet Protocol (VOIP) related networks, products, and services.
Similar to the North American Network Operators’ Group (NANOG), The Voice Operators’ Group seeks to assist in the creation of a robust, stable and growing VOIP ecosystem.
While the topics are definitely not all about security, I would encourage you to join the list if you do anything with the operation of VoIP networks – or if you are just curious to learn more about such networks.