ufw

UFW, or Uncomplicated Firewall, is a command-line utility that provides a simplified interface to manage the Linux kernel’s netfilter firewall through iptables. It is designed to make configuring a host-based firewall easier on Debian-based systems, notably Ubuntu, by abstracting low-level rules into straightforward commands.

UFW uses a small set of commands to add or remove rules, set default policies, and query status. Typical operations include enabling or disabling the firewall; allowing or denying traffic by port or service (for example, ufw allow 22/tcp or ufw deny from 192.168.1.0/24); and applying rate limits to mitigate brute-force attempts (ufw limit ssh). It supports both IPv4 and IPv6 and can use profiles for common applications stored under /etc/ufw/applications.d, enabling one-command configuration for widely used services. Rules can be viewed in a numbered format to facilitate edits, and logging can be configured with ufw logging.

UFW is designed as a front-end for iptables and integrates with the system’s netfilter framework. It is commonly used on server and desktop installations to enforce basic security boundaries with minimal complexity. A typical setup is to set a default deny policy for incoming traffic, allow essential services such as SSH, and permit outgoing connections as needed.

Configuration and files include the main settings in /etc/ufw/ufw.conf and default options in /etc/default/ufw. User rules reside under /etc/ufw, while the before.rules and after.rules files define how rules are applied during processing. Logs are written to /var/log/ufw.log (or the system log depending on configuration). The project also provides optional GUI tools like gufw for users preferring a graphical interface.

Because UFW is a front-end, it is not a replacement for a full firewall policy engine. For complex or highly customized rules, administrators may prefer managing iptables or nftables directly. Always test changes and confirm remote access before enabling the firewall on remote systems.