Massive Spam Increase

I was reading a post by Ed Bott about a recent increase in e-mail spam.  It prompted me to go look at the stats from our anti-spam provider appriver.  They were quite interesting to say the least.  If you look at the screenshot you can see that our email/spam level has increased almost 3x this month alone.  That peak is on Oct 24, on that date we had almost a total of 40,000 emails and at least 30,000 spams.  It has dropped off again, so I can't explain the spike at all?