Block bad referers
What is a referrer?
When you type the address of a site in the address bar of the browser, there is no referer, it's a direct access.
The referer is the site from which you arrive. If you make a request in a search engine, for example on Google, by clicking on a link in the results, the referer will be "google.com".
If my site has a link from a malicious site, then I can decide to block these visits. Let's say that "evil.ru" links to my site example.com?fake_parameter=porn then I want to block "evil.ru".
What is the "Spam Referer"?
The "spam referrer" is a technique of link spamming in order to make a site appear in the logs or statistics as a referrer site.
When consulting your visit statistics, you will be tempted to click on the referring site in order to check where the traffic comes from (which are often bots). You will then be redirected to malicious sites, advertising banners, pornographic sites, credit sites... Blocking spam referer allows you to better follow your traffic statistics, your conversion rates with more reliable data.
How to block bad referrers?
Add an address per line in the Referers List section.
Google in the "Search Console" tool provides the list of links pointing to your site.