CSF (ConfigServer Security & Firewall) is a configuration script for iptables with advanced security features, often used on web hosting servers.

wget https://download.configserver.com/csf.tgz
tar -xzf csf.tgz
cd csf
sh install.sh
    

Configuration: Edit /etc/csf/csf.conf to adjust ports, TCP_IN, TCP_OUT, and enable Login Failure Daemon (LFD).

sudo csf -r   # Restart CSF after changes
sudo csf -a 203.0.113.5  # Allow IP
sudo csf -d 198.51.100.7  # Deny IP