UFW Basics
Date: 2023-10-15
Category: Tutorial
On Debian and Ubuntu systems, the easiest way to configure a firewall is with UFW - The Uncomplicated FireWall.
Installing and enabling
sudo apt install ufw
sudo ufw enable
The default configuration is to deny all incoming traffic
Listing rules
sudo ufw status
Allowing a service
To enable a service, either type the service name (eg ssh or http/https) or the port number
sudo ufw allow ssh
sudo ufw allow 1234
Deleting a rule
To delete a rule, type delete before the rule, for example
sudo ufw delete allow ssh
Blocking an IP
All ip's can be changed to CIDR ranges (ie 172.16.0.0/24)
sudo ufw deny from 1.2.3.4
Allowing an IP
sudo ufw allow from 1.2.3.4
Changing the default behavior
By default, all incoming connections are blocked unless a rule to allow them is specified. It is not recommended changing this behavior, but if you must, this is how:
sudo ufw default allow incoming
to revert back,
sudo ufw default deny incoming
(you can change incoming to outgoing if you want to change the default behavior for outgoing traffic.)