It seems to be possible to completely hide files inside a shared directory in a virtual machine.

POC (tested in VirtualBox 4.3.10, emulating Debian Linux 3.2.0)

$ cd shared_folder $ cp /bin/ls ls $ mv ls $(python -c "print '\xff'") $ ls -a . ..

but the file is there and can be executed!

$ ./$(python -c "print '\xff'") --help Usage: ./� [OPTION]... [FILE]... List information about the FILEs (the current directory by default). ...

Also, you can't autocomplete its name in your terminal nor delete it with a pattern (like: rm *)