A BINARY COMPUTER VIRUS “is a virus that carries one part of a double payload. Two strains of the virus exist, A and B. Both strains are innocuous in isolation but when they meet, the payloads combine to produce a malicious function.”
https://books.google.com/books?id=_VLmBwAAQBAJ&pg=PA47&lpg=PA47&dq=computer+virus+metabolism&source=bl&ots=VZ5Xit6TPg&sig=2EBk5kG-yFSqUID0C-MnUht1dPc&hl=en&sa=X&ved=0ahUKEwi51qLC35fLAhUBcj4KHQW-B9AQ6AEIDDAB