Referrer spam is a blackhat SEO tactic that allows spammers to promote their websites, web content, programs, and services by mixing useless referrer information into their target’s Google Analytics data.
How to block referrer spam in Google Analytics
1. Open your Google Analytics account and go to the Admin tab.
2. Under the account section click All Filters.
3. Click the + ADD FILTER button.
4. Put the referrer spam website URL as a name for the Filter.
5. Select Filter Type Custom. In Filter Field, find and select Campaign Source. In the Filter Pattern text box, write the referrer spam website URL and click the Save button on the bottom of the page.