[mod_python] differentiate from where comes the request to a file

Is it possible to differentiate between a request to a file of type
(pdf,png, etc) made by a psp page and a direct request made by a user who is
trying to access directly to this files?

Sorry  if it is confuse. The purpose here is to only give access to files
for users who have authenticate to the application, but Even those users
will only have access to files that show up in the application(webpage). And
if those users are trying to guess file names they ill not have access to
the files.
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