ntfs has support for so called ADS (alternative data streams), where one file
may contain multiple files. See http://www.heysoft.de/nt/ep-lads.htm for a free
program to list files which contain such streams. The windows API has support to
list these.

You can create an alternative data stream on nt like this:

echo you can read this > test.txt
echo but not this > test.txt:cantsee

via smbclient or smbfs this alternative stream cannot be listed but one can open
a file called "test.txt:cantsee".

It would be nice if smbfs and smbclient would have an option to enable this ADS
to be shown.

Also creating an ADS on a samba share does not work, the samba server should be
able to handle such bla:foo files the way NT servers do.