BruteProtect is a cloud-powered Brute Force attack prevention plugin. We leverage the millions of WordPress sites to identify and block malicious IPs.

BruteProtect tracks failed login attempts across all installed users of the plugin.  If any single IP has too many failed attempts in a short period of time, they are blocked from logging in to any site with this plugin installed. Once the plugin is installed, you’ll need to get a free BruteProtect API key, which you can do directly from your WordPress dashboard.

The plugin allows you to protect yourself against traditional brute force attacks AND distributed brute force attacks that use many servers and many IPs and even supports Multisite Networks.

via About | BruteProtect.