It was hard to believe, but the student insisted it was true. He had discovered that compact discs from a major record company, Sony BMG, were installing dangerous software on people’s computers, without notice. The graduate student, Alex Halderman (now a professor at the University of Michigan), was a wizard in the lab. As experienced computer security researchers, Alex and I knew what we should do: First, go back to the lab and triple-check everything. Second, warn the public.