Security hardening is a process to secure the system which reduce the attack surface, eliminate unnecessary risk.

...Allow only necessary management PC.

(Will add later)

use SSH key instead of password

(Will add later)

Disable SSH after troubleshooting

(Will add later)

sudon blocking

(Will add later)

https://docs.fortinet.com/document/fortigate/6.4.0/hardening-your-fortigate/612504/hardening-your-fortigate