A firewall is a device that controls access. The basic concept of the firewall is, that nothing gets through unless you say it does. The primary rule on a firewall should be no access. The other rules then sit on top of that main rule, one by one creating opening s just for the ports and the services that you wish to authorize. If you do not explicitly allow something to traverse the firewall, then it will not be allowed through.
Control should be maintained over what ports are granted the right to pass the firewall.
Additions should not be made to the existing rule sets without permission from a security manager. Procedures should be put n place that allow the review of, and authorization or rejection of, requests made to open ports or services up on a firewall. This maintains security by imparting checks and balances into modifications of the rules that the firewall uses to govern its operation. It may seem like a tedious process, but reviewing each rule change can help curtain a devastating mistake. A single opening of a port to outside access can allow a server to be hacked, which can then be used as a springboard to gain access to other networked computers.
Procedures often are perceived as red tape and as an inconvenience, but a few minutes up front can save hours of work by ultimately preventing a great deal of damage. Rules exist obviously for the greater benefit, and just as a firewall has rules, so should the operation procedures centered on its management. The firewall is more than just a device that’s settings affect itself; they affect ever y single server and workstation that sit behind it, depending on it for protection from harm and intrusion by outside systems, viruses and hackers.