Mastering Linux Security and Hardening

Basic usage of ufw

ufw is disabled by default, so you'll need to enable it:

donnie@ubuntu:~$ sudo ufw enableCommand may disrupt existing ssh connections. Proceed with operation (y|n)? yFirewall is active and enabled on system startupdonnie@ubuntu:~$

To do this, I logged in to the virtual machine remotely from a terminal of my trusty OpenSUSE workstation. It gave me a warning that my Secure Shell connection could be disrupted, but that didn't happen. (It could be because of connection tracking rules, or it could be that I just got lucky.) I'll leave it up to you to do a sudo iptables -L, because ufw creates a very large default ruleset that would be impossible to display in this book.

Next, let's add a rule that will allow us to remotely connect ...