Block Referer Spam in NGINX ( blogpost detailing the process http://fadeit.dk/blog/post/nginx-referer-spam-blacklist )

blacklist.conf

# /etc/nginx/blacklist.conf

map $http_referer $bad_referer {
    hostnames;

    default                           0;
    "~social-buttons.com"             1;
    "~semalt.com"                     1;
    "~kambasoft.com"                  1;
    "~savetubevideo.com"              1;
    "~descargar-musica-gratis.net"    1;
    "~7makemoneyonline.com"           1;
    "~baixar-musicas-gratis.com"      1;
    "~iloveitaly.com"                 1;
    "~ilovevitaly.ru"                 1;
    "~fbdownloader.com"               1;
    "~econom.co"                      1;
    "~buttons-for-website.com"        1;
    "~buttons-for-your-website.com"   1;
    "~srecorder.co"                   1;
    "~darodar.com"                    1;
    "~priceg.com"                     1;
    "~blackhatworth.com"              1;
    "~adviceforum.info"               1;
    "~hulfingtonpost.com"             1;
    "~best-seo-solution.com"          1;
    "~googlsucks.com"                 1;
    "~theguardlan.com"                1;
    "~i-x.wiki"                       1;
    "~buy-cheap-online.info"          1;
    "~Get-Free-Traffic-Now.com"       1;
}

mysite.conf

# /etc/nginx/sites-enabled/mysite.conf

# Add the below condition to the sites where you want to block referer spam.
server {
  # ...

  if ($bad_referer) { 
    return 403; 
  } 

  # ...
}

nginx.conf

# /etc/nginx/nginx.conf

# Your nginx.conf file is definitely bigger than this. Just add include line in there
http {
# ...

  include blacklist.conf;

# ...

}