phranque - 9:55 am on Aug 31, 2011 (gmt 0)

you can use mod_rewrite to internally rewrite urls (usually) based on matching the patterns of various environment variables (requested urls, query strings, hostnames, etc.)
if coded properly the internal rewrite will not expose the rewritten url.

however, you can't really restrict or exclude unwanted visitors by hoping to keep a url secret.
the only control you have is providing the response that is appropriate to the visitor-supplied request headers and cookies for the requested url.

how do you identify or recognize that certain group of people?