Idea of this plugin is simple. On failed login attempt – report IP of visitor to centralized database. If same IP fails a lot (no matter on which site) – it will be listed on blocklist.
CSF (Config Server Firewall) allows you to put URL which contains list of IPs, that should be blocked. Set it to our address and your server will be protected from those, who abuse WordPress sites login forms.
Plugin is simple and I believe it can become an effecient tool fighting against hackers, as it would stop bad guys at firewall level, not letting them do any harm.