Over the weekend, my company got hit with CryptoWall. It made its way in through a machine in one of our departments. Sophos, however, was unable to stop it. Fortunately, we've isolated the machine and restored files that were made unusable by the infection. I'm nuking the user's machine to be certain the infection is gone. This certainly could have tunred out a lot worse than it did.
Tell me your horror stories. What's the worst infection that you've had to deal with on your network? How did it get in? What did you do to take care of it? What have you done to prevent it from happening again?