Synology network backup - how is it implemented?

There's a "Backup to remote rsync-compatible server" option in the Synology Disk Station 2.2 firmware. Question is - how to really use it and how is it implemented? How about security and accounts? Can anyone use the rsyncd? Those are some questions for start...

Once you enable the "Network backup service", one more share is created in the "Shared folders" --- there's a NetBackup share now. You can also use the GUI to modify access to the folder based on uid/gid. As there is the option to "use rsync compatible remote server" let's look around for the rsyncd cfg files on the DiskStation (via terminal access).

There's an /etc/rsyncd.conf and /etc/rsyncd.secrets. The rsyncd.secrets lists root with a password hash, the configuration file lists NetBackup rsync module with root user allowed to login. There's a rsync process running as a daemon on the station.

The default setup of the station therefore only allows root user to connect via the normal rsync remote method (no ssh) to the NetBackup module. No data encryption, MD4 based challange-response authentication and the GUI settings aren't reflected in the configuration files --- they only alter the filesystem permissions.

This is ok for a closed network setup --- but questionable on an open network.