CSF stands for ConfigServer Security & Firewall, it is Server Firewall created to provide better security for your server while giving you an easy to use, advanced interface for managing your firewall settings. CSF configures your server’s firewall to lock down public access to services and only allow certain connections, such as logging in to FTP, checking your email, or loading your websites. CSF is a Stateful Packet Inspection (SPI) firewall, Login/Intrusion Detection and Security application for Linux servers. It can protect your server against attacks and improve security. In this article you will learn how to install and configure CSF firewall on your linux servers.
Step 1: Install CSF dependencies
Run below command to install CSF dependency.
# yum install perl-libwww-perl -y
Step 2: Download and install CSF
Use below commands to download CSF
# Yum install wget -y # cd /usr/src # wget https://download.configserver.com/csf.tgz
Now extract files and install CSF using below commands
# tar xzf csf.tgz # ls # cd csf # sh install.sh
Step 3: Configure CSF
Before any configuration changes, you need to disable default or any installed firewall on the server. In my cas I have default firewall application “firewalld”
Disable firewalld using below commands
# systemctl stop firewalld # systemctl disable firewalld
Now configure CSF firewall
Open CSF Configuration file /etc/csf/csf.conf using below command and change Change TESTING = “1” to TESTING = “0” as you can see in below image.
# vi /etc/csf/csf.conf
Now restart, enable and test CSF
# systemctl restart csf
# systemctl restart lfd
# systemctl enable csf
# systemctl enable lfd
# systemctl is-active {csf,lfd}
# csf -v
Step 4: CSF Management
Open ports in CSF Firewall
Open csf.conf file using below command and add desired ports under Allow incoming ports or Allow outgoing ports.
# vi /etc/csf/csf.conf
# Allow incoming TCP ports TCP_IN = "20,21,22,25,53,110,143,443,465,587,993,995,80"
# Allow outgoing TCP ports TCP_OUT = "20,21,22,25,53,110,113,443,587,993,995,80"
Now restart the firewall to apply new changes.
# csf -r
Block and Unblock an IP address
Command to block an IP address
# csf -d IP-ADDR
Command to unblock an IP address
# csf -dr IP-ADDR
Allow and remove an allowed IP address
Command to allow an IP address
# csf -a IP-ADDR
Command to remove an allowed IP address
# csf -ar IP-ADDR
Below are the some useful CSF commands to mange your server security.
