Your question is not clear to me.
If you mean not displying on the screen, you can do this theough the setup or chANGE THE SKIN.
If you mean for others to see on the network, some imges have the ability to disable FTP.
If you are connected to a server, the server provider needs may need this.
You can always enable firewall in your router.
And change password on your dreambox.
Do not forget to disable samba.