You wouldn't believe this, but I was just writing a bunch of articles on this. It's called ghost referrer spam. It's traffic that doesn't usually go to your site, it just shows up in your Google Analytics data for webmasters to see (they want you to visit the URL). Since the traffic doesn't actually hit your site, you can get rid of it by applying a filter in Google Analytics.
1. Log Into Your Google Analytics Account
2. Go To Your ?Admin? Tab
3. Click On ?Filters? Under The ?View? Section
4. Click On ?+New Filter?
5. Enter (insert spam URL) as the filter name, select ?custom? as the filter type, select ?campaign source? as the filter field, enter (insert spam URL) as the filter pattern, and click save.
There are a few other methods you can try, although I haven't personally tried them, so they may or may not work (they probably don't since this is more of an issue with Google Analytics than it is for your site). For example, you could try using this code in your htaccess:
## SITE REFERRER BANNING
RewriteCond %{HTTP_REFERER} spamsite.com [NC,OR] RewriteRule .* ? [F]
This next one is called Deflecting and I got it from Raventools. You basically create a text file called deflector.map with this in it:
After that, you put this in your htaaccess file:
RewriteMap deflector txt:/path/to/deflector.map
RewriteCond %{HTTP_REFERER} !=""
RewriteCond ${deflector:%{HTTP_REFERER}} =-
RewriteRule ^ %{HTTP_REFERER} [R,L]
