Firewall Configuration
All of our installation, except for the PBX in a Flash, comes with apf firewall pre-installed. The number of port open may or may not be sufficient for your requirement. You are free to change them. You may also replace it with other firewall. You may do so since you will be granted a root access.
Please note that it is your responsibility to keep your server secure.
Here are some information about apf http://www.rfxn.com/projects/advanced-policy-firewall/
For PBX in a Flash, please refer to "Firewall Configuration" in the PBX in a Flash specific FAQ.
UPDATE:
As of 1/10/2011 any new server and rebuild server will have combination centos iptables firewall and fail2ban