Asterisk Hacking provides detials of techniques people may not be aware of. It teaches the secrets the bad guys already know about stealing personal information through the most common, seemingly innocuous, highway into computer the phone system. This book provides detials to readers what they can do to protect themselves, their families, their clients, and their network from this invisible threat. Power tips show how to make the most out of the phone system for defense or attack.
This book might be a bit too advanced for me. Still trying to understand IP telephony and get my IP-PBX "Watson" up and working.
I think I'm going to focus more on FreePBX and "PBX in a Flash" studying. This book is a bit too low level for my current skills & interests. Additionally, lots of good resources & PDF's are available online, and the topic is changing so much.