UFW (uncomplicated firewall) is a firewall configuration tool pre-installed in Ubuntu 20.04 that runs on top of iptables. It is easy-to-use and reliable firewall interface. It supports IPv4 and IPv6 versions of Ubuntu.
Installation of UFW
If UFW is not available in your machine. Install it fir by running this command.
sudo apt install ufw
You can enable/disable the UFW service every time the system boots up via the following command:
sudo ufw enable
sudo ufw disable
sudo ufw status
Block Incoming and Allow Outgoing Data Traffic
To block any incoming and allow outgoing data traffic, type this command:
sudo ufw default allow outgoing
sudo ufw default deny incoming
Add, Modify, and Delete Firewall Rules
You can add, modify, and delete firewall rules using two different methods, port number or service name. Type this commands:
To view the list of rules in ufw
To allow a specific rule
sudo ufw allow http
To allow a specific rule
sudo ufw deny http
To delete a specific rule
sudo ufw delete allow http
Advanced UFW Rules
You can grant or prohibit access to a certain IP address. To authorize the IP address to access the services, run the following command:
To allow specific ip address
sudo ufw allow from 162.197.1.100
To deny or block specific ip address
sudo ufw deny from 162.197.1.100
When properly configured, UFW is a powerful tool that may dramatically improve the security of your servers. This reference guide goes over some of the most frequent UFW rules for configuring a firewall on Ubuntu.
By modifying parameters like the source IP address and/or destination port, most of the instructions in this book can be customized to match different use cases and scenarios.
Reference
https://www.digitalocean.com/community/tutorials/ufw-essentials-common-firewall-rules-and-commands
https://linuxhint.com/advanced_ufw_firewall_configuration_ubuntu/
https://www.cyberciti.biz/faq/how-to-configure-firewall-with-ufw-on-ubuntu-20-04-lts/