UFW

UFW (Uncomplicated Firewall) is a streamlined command-line interface for managing netfilter iptables on Linux systems.

UFW simplifies the complexity of iptables by providing a clean, intuitive syntax for securing Linux servers. It defaults to a deny-all incoming policy, allowing operators to open specific ports (like 22 for SSH or 443 for HTTPS) with single-line commands. Originally developed for Ubuntu 8.04 LTS, it remains the standard tool for managing host-based firewalls across Debian-based distributions. Its strength lies in its predictability: you can enable rate limiting to thwart brute-force attacks or restrict traffic to specific IP ranges without writing verbose netfilter rules.

https://launchpad.net/ufw