Yep. The best technique is to pretend as though the file does not exist. Use the same type of request, such as 301 move, regardless of whether or not they've found the correct config file, or a file that doesn't exist. That way they will never know, unless of course they crack your code - which still makes it tougher, if they've found a config file or not.

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The man who comes back through the Door in the Wall will never be quite the same as the man who went out.