Let’s say you have access to a remote machine and use it to copy backups occasionally, eg with rsync. Your local machine has credentials stored that allow write access on the remote machine, however if the local account was compromised that could also allow access to the remote machine and the data stored there.
How can you grant access to an account to write remotely, but also protect the data from this account? One possibility could be to change the permissions on the data after it is copied to prevent deletion/interference, although I’m just making this up. Is there a standard practise for this?
The reasoning is that your backup server should be more secure than production. Production has to have a bunch of stuff open in order to be useful and convenient. The backup server does not. It can be basically fully locked down.
To add - by doing pulls the backup server uses different credentials to run than the credentials used to perform pulls.
Backup server has it’s own credentials database, machines being backed up have their own database. Backup service in backup server uses appropriate credentials from machine being backed up to access the data there (shares, etc). So credentials from compromised machine are unrelated to credentials for backup server.
And if backups are done properly (full on a schedule, daily incrementals, or something similar) you should be able to revert to a known-good state with minimal data loss.