Login Lock - custom WordPress mu-plugin

<?php
/*
Plugin Name: Login Lock
Plugin Description: Tries to prevent automated bruteforce attacks on your WordPress site. Put this file in your "wp-content/mu-plugins/" directory. Then change the value for "LL_NONCE_KEY" and "LL_NONCE_VALUE" to something else. Then go to your wp-login page - for instance http://mydomain.com/wp-login.php?LL_NONCE_KEY=LL_NONCE_VALUE - but of course don't forget to replace "LL_NONCE_KEY" and "LL_NONCE_VALUE" with the actual values that you've set.
*/

// The $_GET key that will be used in the URL
define( 'LL_NONCE_KEY', 'mysecretkey' );
// The value for the above $_GET key. Please don't use the equals("=") or sharp("#") signs here
define( 'LL_NONCE_VALUE', 'myv3ry53cr37n0nc3' );

// Checks whether we're on the login page.
function ll_is_login_page() {
    return stripos( $_SERVER['SCRIPT_FILENAME'], 'wp-login.php' ) !== false;
}

if ( ll_is_login_page() ) {
    if ( ! isset( $_GET[ LL_NONCE_KEY ] ) || $_GET[ LL_NONCE_KEY ] != LL_NONCE_VALUE ) {
        wp_die( 'Unauthorized access!' );
    }

    wp_enqueue_script( 'jquery' );

    // Adds some JavaScript that will change the links and the form's "action" attribute to reflect
    // the proper values so you don't get "Unauthorized access!"
    function login_lock_login_footer() {
        if ( isset( $_GET[ LL_NONCE_KEY ] ) && $_GET[ LL_NONCE_KEY ] == LL_NONCE_VALUE ) { ?>
            <script type="text/javascript">
                (function($){
                    $(document).ready(function(){
                        $('form').attr( 'action', add_query_args( $('form').attr('action') ) );
                        $('body a').each(function(){
                            $(this).attr( 'href', add_query_args( $(this).attr('href') ) );
                        });
                    })

                    function add_query_args( url ) {
                        // Don't add the arguments twice - just in case
                        // Also add the arguments only to wp-login.php related links
                        if ( ! has_query_args( url ) && url.indexOf( 'wp-login.php' ) !== -1 ) {
                            var args = '<?php echo esc_js( LL_NONCE_KEY . "=" . LL_NONCE_VALUE ); ?>';
                            if ( url.indexOf( '?' ) !== -1 ) {
                                url += '&' + args;
                            } else {
                                url += '?' + args;
                            };
                        };

                        return url;
                    }

                    function has_query_args( url ) {
                        return url.indexOf( '<?php echo esc_js( LL_NONCE_KEY . "=" . LL_NONCE_VALUE ); ?>' ) !== -1;
                    }
                })(jQuery)
            </script>
            <?php
        }
    }
    add_action( 'login_footer', 'login_lock_login_footer', 10 );
}