Защита изображений от хотлинка nginx

#### IMG protect ###

valid_referers none blocked ~($server_name)
 ~(buildsiteblog|yandex|google|yahoo|bing|facebook|subscribe|feedburner|mail|rambler|nigma|ask|qip|bing|ukr.net|twitter);
        if ($invalid_referer) {
                return 403;
        }
#####

nginx