[Plugin: Statpress Visitors] Blocking Referer from Displaying Certain Websites?

Sorry to reply late but WordPress.org does not report to the developer that there is a new post!
What you can do is edit the file located in the directory spider.dat wp-content/plugins/statpress-visitors/def by adding a line like this:

Spam Bot Unknown | spammer’s domain name |

  or any other subject in the referrer spammer, and it will be counted as a spammer and not as a visitor.

But the best solution is to prevent robots to spam comments on your site using effective anti-spam plugins.

You must test them one by one.