It is possible with samba. The thing is, Windows can then get confused because it _expects_ to see all shares and does not (always) update the share list when the authentication changes. So: Linux and Samba can do it (client and server) but don't expect Windows clients to behave properly.
Since the WD NAS run Linux, you can enable this by enabling SSH support and adding "hide unreadable = yes" in the /etc/samba/smb.conf file under the [global] section. (If you need more detailed instructions than this, just tell me.)