Over the past week we have been reporting strange patterns where traffic just stops cold. Our serps look fine, but traffic is sparse and the little making it's was through is not producing.
Our knee jerk reaction is to blame Google, but after reporting my observations to my web host, they finally opened up and released a statement. This is affecting "virtually every web host in existence".
Please read this article and take appropriate action: change your WP password immediately and update to the latest version and plugins. I have suspended all non essential hosts until this blows over...if ever!
Global Wordpress Brute Force Flood 4/11/2013 : [blog.hostgator.com