Netfilter is a kernel module, built into the kernel, that actually does the filtering. Iptables is the userspace module, the bit that you, the user, interact with at the command line to enter firewall rules into predefined tables.

That won't completely solve your problem but it will give you more control in the meantime.CentOS has an extremely powerful firewall built in, commonly referred to as iptables, but more accurately is iptables/netfilter. # iptables-save > /etc/sysconfig/iptables

If the rules in the file are the rules that are loaded upon reboot, then configure your ruleset how you want it and overwrite the file using iptables-save as root: If you can't find where the ruleset is being loaded from, you can look at the system's default ruleset /etc/sysconfig/iptables and compare it to the loaded rules using: $ sudo iptables -vnL Or even one level higher $ sudo grep -r iptables /etc* You can try searching through all of your system's initialization scripts for iptables commands using: $ sudo grep -r iptables /etc/rc* Any commands in the file are executed during bootup so it's possible the iptables commands are in there. Adding commands to the file /etc/rc.local is one such method. Stopping iptables from starting during bootup using chkconfig would normally solve your problem, however since you mentioned that you had some 'Cyber Security' people work on your server it's possible that iptables is configured to start using a non-standard method.

Restart iptables