UFW
ufw is an uncomplicated firewall used to block and allow traffic
Installation
You can install ufw with apt
apt install ufw
Using ufw
To allow or deny ports you can use following commands
ufw allow 22 # to allow port 22
ufw deny 53 # to deny port 53
You can later start and enable ufw
ufw enable
To see status of ufw you can use the following command
ufw status
Status: active
To Action From
-- ------ ----
22 ALLOW Anywhere
53 DENY Anywhere
22 (v6) ALLOW Anywhere (v6)
53 (v6) DENY Anywhere (v6)