For the media library you can use the pre_get_posts hook targeting upload.php by means of $pagenow, a global variable, or even better, because globals are the devils child, by means of get_current_screen(). I’m assuming you want to target the media modal tab too – because targeting only one, but not the other, doesn’t make much sense after all -, you can do that via the ajax_query_attachments_args hook.
