# block visitors referred from semalt.com
RewriteEngine on
RewriteCond %{HTTP_REFERER} semalt\.com [NC]
RewriteRule .* – [F]
# End semalt block
# block referer spam buttons for website
RewriteEngine On
RewriteCond %{HTTP_REFERER} buttons\-for\-website\.com
RewriteRule ^.* - [F,L]
# End buttons for website block
# from http://www.specializeddigitalmarketing.com/block-semalt-buttons-website-bots/