"There is an informational entity known as the metavirus, which causes information systems to infect themselves with customized viruses. This may be just a basic principle of nature, like Darwinian selection, or it may be an actual piece of information that floats around the universe on comets and radio waves—I'm not sure. In any case, what it comes down to is this: Any information system of sufficient complexity will inevitably become infected with viruses—viruses generated from within itself.