This is a dead-simple module that ensures that Drupal always returns a 404 "Not Found" error instead of returning a 403 "Access Denied" error.
Why would you need this?
- Your Security team doesn't want the server to give away the presence of paths that users don't have access to.
- You are paranoid.
This is basically the opposite of any sort of upsell type module, like r4032login or logintoboggan where you display login forms when a user is denied access to content. This tells your users that things they don't have access to aren't there at all.