Blocking semalt referral

if you dont know what am talking about.. read up on it here

http://www.straight.com/blogra/593201/homeless-vancouver-referrer-madness-wordpress-finally-flags-semalt

referral shows up as semalt.semalt.com in google analytics

I have added the following to my web.config IIS and site reset still does not block this cancer.

below is whats in my web.config.. 

I would appreciate some help to kick this off my site (they are on my site day and night, using my bandwith)

<system.webServer><rewrite><rules><rule name="RequestBlockingRule1" patternSyntax="Wildcard" stopProcessing="true"><match url="*" /><conditions><add input="{HTTP_REFERER}" matchType="Pattern" pattern="semalt.semalt.com" ignoreCase="true" negate="false" /></conditions><action type="AbortRequest" /></rule></rules></rewrite></system.webServer>