Digital Ocean now offers free firewall for customers
Many cloud providers offer free or paid firewalls to help customers protect their virtual infrastructures. Now Digital Ocean does too.
There are two relevant posts on Digital Ocean that will tell you what you want to know about them, and will walk you through the setup process. One is an introduction to digitalocean cloud firewalls, and the other is a Digital Ocean blog post about them.
I seen no value added in re-writing what's on those pages.
I'm posting this article to let you know the services exists and to encourage you to use it to protect your VM's.
I set it up for mine, and it was pretty straight forward.
Remember to allow SSH and test access to any desired services before assuming it's all working as intended.