Block referer spam in Nginx

bad_referers.conf

map $http_referer $bad_referer {
    default                                0;
    "~semaltmedia\.com"                    1;
    "~100dollars-seo\.com"                 1;
    "~buttons-for-your-website\.com"       1;
    "~best-seo-offer\.com"                 1;
}

# Server block
# if ($bad_referer) {
#     return 444;
# }