Wordfence is a WordPress plug in that provides security against hacks by scanning your intallation for security holes so you can take corrective action in advance before a sadistic hacker does. In addition Wordfence logs login attempts. This allows you to review each attempt and if the login looks to be suspucious you can block the ip address. Wordfence also provides for performance boosts using a unique caching system. This video however is all about how to identify and block a susucions login attempt.