Blocks access to referral spammers.
Add's a rule for each known referral spammer to the .htaccess file.
Currently spammers list is updated trough a text file, in the future this could be done by collecting them from a server.
On install a few default lines will be added to the .htaccess, do not alter or remove them or the module will not work.
You can add custom rules, they wont be overwritten.
Impact van Referral spam in Google Analytics