"Of course, it's always faster to start by downloading an
existing toolbox that someone else has compiled. For example, check
out the SecureLogix VoIP Assessment Tools archive (above,
right)—a zip file containing source code for dozens of tools
developed by David Endler and Mark Collier, authors of Hacking
Exposed: VoIP (ISBN: 0072263644). Or download and burn a LiveCD of
a general-purpose penetration test toolkit like BackTrack3—a
bootable Linux environment that includes roughly 30 VoIP and
Telephony analysis tools"