This is a sample of code which aids me to block spam referrers via .htaccess on my PR3 website projects.
# [ CP Global Ban – Open ]
RewriteEngine on
Options +FollowSymlinks
RewriteCond %{HTTP_REFERER} super-seo-guru.com [NC,OR]
RewriteCond %{HTTP_REFERER} seoservices2018\.com [NC,OR]
RewriteCond %{HTTP_REFERER} seocheckupx\.net [NC,OR]
RewriteCond %{HTTP_REFERER} foxweber\.com [NC,OR]
RewriteCond %{HTTP_REFERER} free-fbook-traffic\.com [NC,OR]
RewriteCond %{HTTP_REFERER} share-buttons-for-free\.com [NC,OR]
RewriteCond %{HTTP_REFERER} anonymizeme\.pro [NC,OR]
RewriteCond %{HTTP_REFERER} openallurl\.com [NC,OR]
RewriteCond %{HTTP_REFERER} streetwearhypeclub\.com [NC,OR]
RewriteCond %{HTTP_REFERER} anonymizeme\.pro [NC,OR]
RewriteCond %{HTTP_REFERER} openmultipleurl\.com [NC,OR]
RewriteCond %{HTTP_REFERER} weburlopener\.com [NC,OR]
RewriteCond %{HTTP_REFERER} urlopener\.com [NC,OR]
RewriteCond %{HTTP_REFERER} top1-seo-service\.com [NC,OR]
RewriteCond %{HTTP_REFERER} rankings-analytics\.com [NC,OR]
RewriteCond %{HTTP_REFERER} serw.clicksor\.com [NC,OR]
RewriteCond %{HTTP_REFERER} justprofit\.xyz [NC,OR]
RewriteCond %{HTTP_REFERER} burger-imperia\.com [NC,OR]
RewriteCond %{HTTP_REFERER} responsive-test\.net [NC,OR]
RewriteCond %{HTTP_REFERER} video–production\.com [NC,OR]
RewriteCond %{HTTP_REFERER} videos-for-your-business\.com [NC,OR]
RewriteCond %{HTTP_REFERER} buttons-for-website\.com [NC,OR]
RewriteCond %{HTTP_REFERER} wmasterlead\.com [NC,OR]
RewriteCond %{HTTP_REFERER} livefixer\.com [NC,OR]
RewriteCond %{HTTP_REFERER} adspart\.com [NC,OR]
RewriteCond %{HTTP_REFERER} coderstate\.com [NC,OR]
RewriteCond %{HTTP_REFERER} sharebutton\.net [NC,OR]
RewriteCond %{HTTP_REFERER} seopub\.net [NC,OR]
RewriteCond %{HTTP_REFERER} anticrawler\.org [NC,OR]
RewriteCond %{HTTP_REFERER} ranksonic\.info [NC,OR]
RewriteCond %{HTTP_REFERER} ntent\.com [NC,OR]
RewriteCond %{HTTP_REFERER} 7makemoneyonline\.com [NC,OR]
RewriteCond %{HTTP_REFERER} anonymous-redirect\.com [NC,OR]
RewriteCond %{HTTP_REFERER} kambasoft\.com [NC,OR]
RewriteCond %{HTTP_REFERER} srecorder\.com [NC,OR]
RewriteCond %{HTTP_REFERER} 100dollars-seo\.com [NC,OR]
RewriteCond %{HTTP_REFERER} savetubevideo\.com [NC,OR]
RewriteCond %{HTTP_REFERER} semalt\.com
RewriteCond %{REQUEST_URI} !^/[0-9]+\..+\.cpaneldcv$
RewriteCond %{REQUEST_URI} !^/[A-F0-9]{32}\.txt(?:\ Comodo\ DCV)?$
RewriteCond %{REQUEST_URI} !^/\.well-known/pki-validation/[A-F0-9]{32}\.txt(?:\ Comodo\ DCV)?$
RewriteCond %{REQUEST_URI} !^/\.well-known/acme-challenge/[0-9a-zA-Z_-]+$
RewriteCond %{REQUEST_URI} !^/\.well-known/cpanel-dcv/[0-9a-zA-Z_-]+$
RewriteCond %{REQUEST_URI} !^/\.well-known/pki-validation/(?:\ Ballot169)?
RewriteCond %{REQUEST_URI} !^/\.well-known/pki-validation/[A-F0-9]{32}\.txt(?:\ Sectigo\ DCV)?$
RewriteRule .* – [F]
# [ CP Global Ban – Close ]
