DEFINED NICHES. “Some viruses also exhibit predatory behavior. For instance, the DenZuk virus will seek up and overwrite its traces of the Brain virus if they are both present on the same system.”
https://books.google.com/books?id=qErpoKjc1h4C&pg=PA261&lpg=PA261&dq=computer+virus+metabolism&source=bl&ots=NWmF_p3xqj&sig=XEfXy2VQZdbYQgBJSndUVHbkDSI&hl=en&sa=X&ved=0ahUKEwi51qLC35fLAhUBcj4KHQW-B9AQ6AEIFzAE