location ~/admin\.php$ {
allow XXX.XXX.XXX;
deny all;.
auth_basic "Administrator Login";
auth_basic_user_file /path/to/your/password_file;
root /path/to/root/forum/directory;
fastcgi_pass 127.0.0.1:9000;
fastcgi_index index.php;
fastcgi_param SCRIPT_FILENAME
$document_root$fastcgi_script_name;
include /etc/nginx/fastcgi_params;
}