Started off by
- Enabling unattended updates
- Enable only ssh login with key
- Create user with sudo privileges
- Disable root login
- Enable ufw with necessary ports
- Disable ping
- Change ssh default port 21 to something else.
Got the ideas from networkchuck
Did this on the proxmox host as well as all VMs.
Any suggestions?
Block outbound traffic too.
Open up just what you need.
Segment internally and restrict access. You don’t need more than SSH to a Linux Server, or perhaps to it’s web interface for an application running on it.