By default, a Drupal site allows undefined arguments on any system path instead of returning 404 Not Found (e.g. http://drupal.org/node/1/asdlfkjadlfkdjaflakjsldkfa).  I created the Strict 404 module to override this behavior and enforce 404 responses for paths that are not actually defined in the menu system.

Some contrib modules rely on the undefined argument behavior (e.g. for admin pages) so you may want to enable Strict 404 only for certain path patterns (usually vistor-facing pages).  The module provides an admin page for selectively enabling Strict 404 responses.