This is nearly always a question. 99% of Linux users believe that Linux is secure by default. By default, almost all Linux distributions do not have a firewall. To be more precise, they have a dormant firewall. Because the Linux kernel includes a built-in firewall, and theoretically all Linux distributions include one, but it is not configured or active. But don't worry, even without an active firewall, your Linux is still safe. Most distributions, including Ubuntu and Linux Mint, have no open ports by default, ensuring that outsiders cannot access your machine. Nonetheless, I urge that you enable a firewall. It is preferable to be safe than sorry. We will further discuss how to configure the linux firewall using firewall-cmd.