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How to Setup a Firewall on your Cloud Server – CSF / CPanel, and more!   no comments

Feb 21, 2015 @ 12:02pm cloud security

firewallI have a question for you. Does your server have a firewall running on your server? For those who do know what a firewall is, let’s go to our good friend Wikipedia:

‘In computing, a firewall is a network security system that controls the
incoming and outgoing network traffic based on applied rule set. A firewall establishes a barrier between a trusted, secure internal network and another network (e.g., the Internet) that is assumed not to be secure and trusted.’

As avid readers of the blog know, I like to ground these ideas with every day analogies. You can think of a firewall like a door to your home. When the door is opened, people can walk directly into your house. Should you want to keep people out, you close and lock the door. This is the way a firewall works on a server. You place the firewall onto your server to keep intruders from the internet from accessing your data.

Firewalls can be either hardware or software based. If you go with a hardware based firewall, the firewall is connected to your switch that allows for traffic to be filtered upon a rule set you determine. You would use a hardware based firewall if you had a dedicated server. A software based firewall is installed within your server. It still blocks traffic based off rule sets you create, but it just does it from within the server and not out in front like a hardware based firewall.

For the rest of this article, I will provide you the steps to install CSF, which is short for ConfigServer Security and Firewall. This firewall is supported across many different Operating Sytems, RedHat Enterprise, Centos, CloudLinx, Fedore, Virtuozzo, VMWare, to name a few. You can read more about the supporeted systems here:

This firewall can be installed with the following steps on your Linux based server:

mkdir /usr/local/src <– Creates the directory to install CSF

cd /usr/local/src <– Changes your location on the server to the newly created directory

wget <– downloads the CSF software to your server

tar xfz csf.tgz <– Extracts the software
cd csf <– Changes your location on the server to the CSF directory

./ <– Installs the CSF firewall

CSF, when installed, and configured properly, places a preset list of rules onto your server. These rules can be configured directly within the csf.conf file or the csf configuration file. If you have a cPanel based server,  you want to ensure that you have the following ports opened for inbound and outbound:

# Allow incoming TCP ports
TCP_IN = “20,21,22,25,53,80,143,443,465,587,993,995,2078,2082,2083,2086,2087,2095,2096”

# Allow outgoing TCP ports
TCP_OUT =”20,21,22,25,37,43,53,80,110,113,443,465,587,873,995,1167,2086,2087,2089 ”

Those ports cover most of the ports you will need for your cPanel or non-cPanel server to function. You can read more about ports and their functions here:

Once you do that, you may want to limit the amount of connections each user can make to your server. This can be set by changing CT_Limit in your csf.conf to the number of connections you want each user to be able to make. For example, CT_Limit = “150” will only allow each user to make 150 connections to your server.

You may also want to remove port 22 from TCP_IN along with setting your SSHD_config file to do only public_key authentication. Why would you do this? This will lock down your server from the outside and only allow people who have SSH keys installed into your server to gain access using SSH.

CSF can be configured in a multitude of ways to add another layer of security to your server. I highly recommend going to and using the forums to learn more about the many features of CSF and how tweaking the settings can help ensure you’re providing a stable, safe and secure server environment

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Written by Jeremy on February 21st, 2015

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