If someone gets a Network Attached Storage device to backup all the system daily. If ever someone hacks into the server, how is that data protected if the hacker has also access to the NAS (where the backups are done in case of an attack?). since it is attached to that server and he can probably get access to it via the network or in the My Computer. Keep in mind that I am talking about windows 2003 server machiens.

Basically my question is, what is the way to have a daily backup done so that the NAS is completely invisible to the hacker. So that in the case of an Erase-ALL, everything can be restored.