Anti-spam comment system.
https://wordpress.org/plugins/wp-spamfree/
Widgets · WordPress Plugins
Get access to data on 46,531 websites that are WP-SpamFree Anti-Spam Customers. We know of 11,347 live websites using WP-SpamFree Anti-Spam and an additional 35,184 sites that used WP-SpamFree Anti-Spam historically and 6,866 websites in the United States.
Get a list of 46,531 websites using WP-SpamFree Anti-Spam which includes location information, hosting data, contact details, 11,347 currently live websites and an additional 2,439 domains that redirect to sites in this list. 35,184 sites that used this technology previously and 6,866 websites in the United States currently using WP-SpamFree Anti-Spam.