The UFW firewall is the default firewall that ships standard with the Ubuntu Linux Distribution. UFW stands for UncomplicatedFirewall.

• To enable the ufw firewall, open a new Terminal window and execute the following command:
  sudo ufw enable

• To disable the ufw firewall, open a new Terminal windows and execute the following command:
  sudo ufw disable

• To view the status of the ufw execute the below command:

  sudo ufw status
  
  sudo iptables -F  will flush the firewall rules. You won't be able to turn off the firewall as it is built into the kernel.