We do a lot of posts on server protection because honestly — it’s pretty important. This time around we wanted to highlight and breakdown one of the most common tools used to protect your machine: the firewall. In this tips and tricks, we’ll go over what is a firewall, how it works, and why there’s no excuse to not be using one.


What is a firewall? 

Divided into network-based  or host-based, a firewall is a system of protocols and scripts that monitor, scan and protect a network from potentially malicious or hazardous traffic. Essentially, it acts as the gatekeeper for your server or network, permitting and blocking traffic based on a predetermined set of criteria called “rules”. 

A firewall can be installed on an individual server or can function as a stand-alone piece of hardware, known as a perimeter firewall. 


How does a firewall work? 

Internet traffic is transmitted in a series of data packets that travel out from one location (a source IP) toward a final location  (destination IP). If the destination IP is on a firewall protected network, the firewall will inspect the packets to verify whether or not it is allowed to enter the network. Then through a process called filtering, where the machine reads the rules defined by the source IP, destination IP, and the packet itself, the packet will either be “dropped” or “accepted” into the network. 

To illustrate this better, we’ll use a cPanel technical support request as an example. To do our job, our team often has to send information to, or completely enter, a client’s server when resolving an issue. (Depending on the level of access permitted, a server can be completely taken over from a remote machine; an occurrence which, while beneficial for our work, can be hazardous if it were a malicious attacker.)  When a firewall allows packets from our source IP,, then our Technical Support staff will be able to access the server behind that firewall. This access, however, works in both directions and can be used to control access from either source to destination and vice versa.

Why use a firewall? 

1. Block individual or ranges of IP addresses
2. Allow computers in a private network to access the internet
3. To prevent internal users accessing remote sites
4. Limit access only to services running on the server
5. Help to prevent denial of service attacks

Learn more about firewalls and how to configure them for your cPanel & WHM services on our Documentation Site.