Computer viruses and worms haunt the internet. They worm their way into a system, replicate, and spread again. It’s a simple process—with devastating consequences. But there’s a whole industry of people that rose up to fight back. Craig Schmugar recalls how he and his team responded to MyDoom, one of the fastest-spreading worms ever. Dr. Nur Zincir-Heywood reveals the inner workings of viruses and worms, and how they draw their names from the world of biology. And security expert Mikko Hypponen shares advice on avoiding malware. But he also warns that we’re in an arms race against malware developers.