This file is created to prevent referral spam traffic.
It has been spread wide across the web and it causes a great harm to websites. Definitely it harms your rankings, your SEO and Google trust. Add this to your .htaccess file on a Apache server to prevent referral spam traffic from websites like semalt & buttons-for-websites. This file is usually found in the root “public_html” folder of your website.
If this method fails you can prevent referral spam by:
If you'd like to help, just fork the repository, then add useful stuff and send a pull request.