Does Linux have built in firewall?

Ubuntu includes its own firewall, known as ufw – short for “uncomplicated firewall.” Ufw is an easier-to-use frontend for the standard Linux iptables commands. You can even control ufw from a graphical interface. Ubuntu’s firewall is designed as an easy way to perform basic firewall tasks without learning iptables.

Is a firewall necessary?

Protecting your computer from external threads – When using a firewall, you’re protected from cyber threats to a greater extent than without a firewall. The firewall acts as a barrier between your computer and the internet and only lets traffic from trusted and secure sources to communicate with your computer.