Referrer spam has always been a nuisance, specially if you have some traffic restrictions on your hosting. The referral traffic robs your site from the precious bandwidth allocated (also know as Bandwidth Theft). Also with a large number of spam traffic, legitimate users will be greeted with a slow and sometimes non responsive site.
Htaccess enables one to block certain referrer sites and prevent referrer spam. The following post list some techniques to do so. One way to prevent referrer spam is to force a error and stop any further redirection. Note that the following requires that ‘mod_rewrite’ is enabled on your server.