If you're not sure what you're doing, you are much safer running Incredible PBX. No ports are exposed to the Internet!
Im not sure how that's helpful to resolving the problem. Apart from that it's also somewhat untrue. Here are examples of explicit instructions to open ports in/for PIAF:
http://nerdvittles.com/?p=216
"To fix NAT problems with Asterisk, you simply tell your router to forward all data received on UDP ports 4569, 5004 to 5037, 5039 to 5082, and 10000 to 20000 to the private IP address of your Asterisk server."
http://nerdvittles.com/?p=684
"...If the remote site has a fixed IP address, the procedure to allow remote access to your server is fairly straight-forward: just map the SIP ports on the hardware-based firewall to your server (UDP 5000:5082 and UDP 10000:20000) and then restrict SIP access using IPtables to the remote IP address as well as the subnet of your private LAN."
http://nerdvittles.com/?p=66
"Then you'll need to make certain that your firewall redirects incoming UDP traffic on ports 5060 through 5082 and 10000 through 20000 to the internal IP address of your Asterisk server."
As my posts above detail, the only ports open to the outside world are for SIP traffic; moreover, these firewall rules are explicitly defined to accept SIP traffic from Vitelity's domain only. Doing these things is supposed to prevent SIP traffic from other domains/IP's but the evidence in the call logs, at least in my case, shows that these measures were overcome.
The folks that are posting in this thread are obviously concerned about the security of their PIAF installations--and are posting here to assess and fix the problem, and perhaps learn along the way or discover a mistake or misconfiguration. Whether we all "know what we're doing" is beside the point. Ensuring bulletproof network security is a complex, evolving, iterative endeavor and even the most knowledgeable, diligent folks occasionally screw up. Im sure most people would claim to know how to drive a car, but how many of us have been involved in accidents?
Back on point:
I've posted details about my hardware firewall, iptables, and SIP settings. Does anyone have any idea about how are these calls getting through?