安装Add A Firewall to Debian Linux with UFW

What is UFW?

The Uncomplicated Firewall (ufw, and gufw - a Graphical User Interface version of the same) is a frontend for iptables and is particularly well-suited for host-based firewalls. Ufw provides a framework for managing netfilter, as well as a command-line interface for manipulating the firewall. -https://wiki.debian.org/Uncomplicated%20Firewall%20%28ufw%29

1. Log into the Debian device
2. Run the following commands in a terminal window:
   # update software repositories
   sudo apt update
   # install ufw
   sudo apt install ufw -y
   # enable ufw
   sudo ufw enable
   # output the ufw status
   sudo ufw status
   # add some default firewall rules
   sudo ufw default deny incoming
   sudo ufw default allow outgoing
   # if a webserver is running, allow the incoming traffic
   sudo ufw allow 80/tcp
   sudo ufw allow 443/tcp
   # to allow incoming ssh connections, open port 22
   sudo ufw allow 22/tcp
   # output the ufw status
   sudo ufw status
   # to install a graphical user interface for ufw, install gufw
   sudo apt install gufw -y