Good News: Incredible PBX Firewall does NOT expose UDP port 623 to the internet.
It's unrelated news as IPMI/BMC is handled before the OS kernel and since iptables is kernel based the firewall rules really may not even apply here.
Incoming Packet -> BMC listens on UDP 623 accepting that traffic -> OS Kernel -> iptables
If you are on something like ProxMox or a VM host then the IPMI/BMC is at the host level not the guest level meaning all the VMs sitting on ProxMox "not listening on UDP 623 in the firewall" is meaningless since it never gets there.
So the IPMI/BMC stuff is handled before the packet is sent into the OS kernel where iptables lives. Since the packet would never it make it to the kernel, how is the firewall supposed to block it? There may be rare cases where it does make it to the kernel but for the most part it doesn't.
The real ways to deal with this are:
-- External firewall that sits in front of the server and the IPMI/BMC interface
-- Dedicated Out-of-band NIC interface that can be isolated and not routed to the Internet
-- Disabling IPMI-over-LAN
Don't know if your bare metal or VM host (again you need to control the host not just be a guest) will answer on UDP 623 for IPMI/BMC you can run this:
nmap -sU -p 623 <your public ip>
Phone System 