Well yes it is limited:
the mkdir " " just creates a directory with name " ". In a GUI environment you will see a folder with no name. In a text environment those are a bit harder to detect.
the touch .bla creates a file that is "hidden" but you can still list those with ls -al and you can configure your file browser to expose hidden files by default.
So this stuff is pretty easily detectable.
Google lists a bunch of other sites with suggestions. For example: