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?
+1
Use unattended updates ONLY for bug and security fixes, nor for minor or major releases. Ensure you configure your auto-updaters properly!
Debian
unattended-upgrades
only upgrades packages from the main and security repos by default, so it should be fine since no major updates are performed within a particular Debian version.