Kudos to Brian Krebs, whose excellent investigative reporting produced some rather dramatic results.What's the story? McColo Corp. — major source of spam — was knocked offline earlier this week. And now there's a large decrease in the amount of spam being distributed.Why is that? Because McColo Corp. was hosting a large number of spam bot control and command servers. Knocking them offline has left the spam bots temporarily without masters.Unfortunately the bots themselves are still out there, so the spam will eventually return.You can download a very detailed report on McColo from hostexploit.com.