McNulty: The threat is constantly evolving. Most of the things we are intensely worried about today didn't exist 10 years ago. The threat had changed from the kid in the basement trying to impress his friends by defacing a Web site to organized crime and to very competent computer experts trying to steal and to commit crimes. It is happening every day. The FBI's most recent report said that cost of fraud on the Internet to American businesses was $67 billion. That's just the tip of the iceberg, because it is only the amount that people want to own up to. Most importantly, we live in a world where it is all happening in real-time. Ten years ago, it took weeks for things to spread across the globe. Five years ago, it was hours. And now it is in minutes. In the future, it is going to spread even faster. Signature-based defenses designed to prevent [trouble] after the horse has escaped the barn is ancient technology.