Nginx server settings, where only requests to example.com will be processed, and everything else will simply result in a no response.

gistfile1.nginxconf

server {
  listen 80 default_server;
  return 444;
}

server {
  listen 80;
  server_name example.com;

  root /var/www/example.com;
  index index.html;

  location / {
    try_files $uri $uri/ =404;
  }
}