sub-directory protection and search engines

I have been using a low-tech solution to protect sub-directories from casual
browsers by putting a default.html page into every folder that has a meta
refresh back to home.
This prevents users from accessing folder contents at the ISPs that are not
configured to prevent this.
I have a feeling that the search engine robots have been reading these files
and penalizing me.
Is this a possibility - what other low tech solutions are available.

Craig

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