It is recommended to use a simple host firewall and deny any incoming connections on all ports. gufw provides a simple graphical user interface for the Uncomplicated Firewall program.  It is easy to perform common tasks like blocking or allowing P2P, individual, or pre-configured ports.
How-to: Install and Configure a Firewall
The following steps install gufw on a Debian host.
1. Install gufw.
2. Start gufw.
Unlock. Enter the password.
5. Check the settings.
By default, the settings should be
Incoming: Deny and
Although not recommended, it is possible to add special firewall rules, use pre-configured options for common programs and services, or set other advanced options in gufw by following this guide.
For further information on firewalls, see here.
- Uncomplicated Firewall by itself only provides a command-line interface for managing the netfilter firewall.
- The firewall is disabled by default.