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How to Install CSF (ConfigServer Firewall)

ConfigServer Firewall (or CSF) is a free and advanced firewall available for most Linux distributions, which manipulates iptables chains while also providing greater functionality that iptables doesn’t offer. In addition to the basic functionality of a firewall – filtering packets on IP addresses, services, and ports – CSF includes other security features, such as login/intrusion/flood detections. CSF also includes UI integration for cPanel, DirectAdmin, and Webmin.

CSF works by utilizing the Login Failure Daemon (lfd), which provides a tool that scans the latest log file entries for login attempts against your server. This is useful for detecting brute-force attacks, allowing lfd to automatically detect the pattern and block the offending IP. 

*NOTE: These instructions are based on a live document that might change in the future, meaning it’s important to review it prior to proceeding. The instructions from the file have been tested and broken down below at the time of writing this article and include further troubleshooting information that is not present in the live document.

The file can be found in the following link – 

Installing ConfigServer Firewall (CSF)

To install CSF onto your Linux distribution, just follow along with the instructions below. *Note: Be sure to update your packages with package manager to ensure you have the latest versions available to you.

  1. First, in order to install CSF, you must log in to your server with root user.
  2. Next, before downloading CSF, make sure that you have the following packages installed on your system using sudo apt install followed by the name of the packages you’re installing:
    1. perl-libwww-perl and/or libwww-perlc (*Note: some distributions might not require or have these available)
    2. wget
    3. tar
    4. nano
      Screenshot showing the sudo apt install command
  3. Now, navigate to the /usr/src directory
    cd /usr/src
    Screenshot showing the cd /usr/src command
  4. Next, download the CSF installation pack (contained in a compressed tarball) using the following command:
    Screenshot showing the wget command
  5. The downloaded file is compressed, so it has to be uncompressed and extracted before it can be used. To extract the file, use the following command and hit enter.
    tar -xzf csf.tgz
    Command line showing the tar -xzf csf.tgz command used to unpack CSF
  6. Now it is time to execute the CSF’s installer script. Move to the csf directory (by using: cd /usr/src/csf) and execute the following installation script:
    Screenshot showing the results of the sh command
    *Note: If this fails with either an error stating “Can’t locate Net/” or “Can’t locate Math/“, then install perl-Net-SMTP-SSL perl-Math-BigInt and run the CSF installation script again.
  7. Now that CSF is installed, run the following test script to ensure all prerequisites are present:
    perl /usr/local/csf/bin/
    Screenshot showing the results of the perl /usr/local/csf/bin/ command
  8. Assuming that everything is working correctly, the next step is to disable firewalld to reconfigure CSF using the following command:
    systemctl stop firewalld

    followed by
    systemctl disable firewalld
    Screenshot showing the command to stop and disable firewalld
  9. Next, edit /etc/csf/csf.conf to change the value of “TESTING = 1” to “TESTING = 0”. The item is present at the very top of the document.
    *Note: Editing can be completed via nano or vim. Remember to save the file when you’ve finished making the edits.
    Screenshot showing the edits to the CSF configuration file
  10. With your edits complete, the next step is to restart CSF using the following command:
    systemctl restart {csf,lfd}
    *Note: if you receive an error on AlmaLinux 9 or any other distro that says “Can’t locate in @INC“, then the epel-release and perl packages need to be installed.
  11. Now, enable CSF and lfd and check whether the service is active using the following commandS:
    systemctl enable {csf,lfd}
    Followed by
    systemctl is-active {csf,lfd}
    Screenshot showing the commands to enable CSF and lfd
  12. Lastly, you can check if the required iptables modules are available using the following command:
    perl /usr/local/csf/bin/
    Command line showing the perl /usr/local/csf/bin/ command used to check iptables modules
    If no fatal errors are reported, then the firewall should be working correctly.

And there you have it! If you have WHM installed on your server, you can also double-check that CSF is working properly by checking under WHM’s menu >> Plugins >> ConfigServer Security&Firewall.


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