Sentinel is a modern, lightweight replacement for the now-deprecated ConfigServer Firewall (CSF) tool. It provides enhanced security while maintaining simplicity and compliance with email protocols.

Unlike traditional firewalls, Sentinel ensures that malicious or suspicious traffic is blocked without generating bounce messages or backscatter spam. This makes it ideal for servers that send or receive high volumes of email.

Why Use Sentinel Firewall​

Using Sentinel on your cPanel server comes with several advantages:

1. SMTP RFC Compliance Sentinel ensures that when a sending server is denied, it receives a proper DENY response. This prevents miscommunication and ensures your server behaves according to standard email protocols.

2. No Bounce Messages Traditional firewalls or spam blockers sometimes generate bounce messages to the “From:” address when rejecting emails. Sentinel avoids this entirely, reducing spam backscatter and improving your server reputation.

3. Backscatter Prevention Your server sends nothing to the sender, leaving the responsibility of notifying the original sender to the sending server itself. This significantly reduces the risk of your server being blacklisted.

4. Easy Drop-in Replacement Sentinel is designed as a drop-in replacement for CSF, meaning you can install it quickly and maintain familiar management routines.

Installing Sentinel Firewall on cPanel/WHM​

Installing Sentinel is simple and can be done via the command line. Here’s the step-by-step guide:

1. Connect to Your Server​

Log in to your server via SSH as the root user:

ssh root@your-server-ip

2. Install Sentinel​

Run the following commands to install Sentinel:

wget https://github.com/sentinelfirewall/sentinel/raw/refs/heads/main/csf.tgz
tar -xzf csf.tgz
cd csf
sh install.sh

Upgrade from CSF to Sentinel Firewall on a cPanel/WHM server​

To upgrade from CSF to Sentinel on a cpanel server, simply run:

bash <(curl -sSL https://raw.githubusercontent.com/sentinelfirewall/sentinel/refs/heads/main/public/upgrade.sh)

Best Practices for Using Sentinel​

1. Regularly Update Sentinel Use the command below periodically to keep your firewall up-to-date:

   bash

   csf -u

2. Monitor Alerts Sentinel will log suspicious activities. Review /var/log/lfd.log to identify potential threats.

3. Combine with cPanel Security Features Use Sentinel alongside cPanel’s built-in security tools, like cPHulk and ModSecurity, for comprehensive protection.