Most importantly: it must be the backup server that has to log into your computer to backup, and not the other way around. That way, if your computer/server is

Most importantly: it must be the backup server that has to log into your computer to backup, and not the other way around. That way, if your computer/server is compromised, the backups are still there. If you make the error to connect to the backup server, a hacker could also log into it and delete everything. I my backup server uses rsnapshot and you can only log into it with ssh + key + OTP.