Restricting access to nodes based on URL

Hi Guys,
Quick question, is it possible to restrict access to particular pages in Drupal based on the URL.

For example, if the following word "internal" appears in the URL eg. http://localhost/internal/my_internal_file.html then have Drupal redirect to the login screen before allowing the user to access the page?

Has anyone come across this before? Would something like this be done through htaccess or using a custom module?

Thanks.