Have you ever set-up Pathauto and then thought to yourself, is there any way to block users from accessing content by it's unaliased path?
To put it another way, say that you have a node (node #10) and it has an aliased path of "content/my-super-awesome-page". How do you prevent users from accessing it via "node/10"?
This is a simple module that does just that. Basically, if it detects that the current page has an alias but the page was accessed using it's internal path, it denies access.