Bacteria are plagued by their own viruses, known as phages. But some species have turned these enemies into allies. By adding the viruses’ DNA into their own genomes, they have become superbugs. These domesticated viruses provide them with new ways of establishing large communities, tolerating harsh environments and shrugging off antibiotics. But we could use these alliances to our advantage. By blocking the proteins produced by the tame viruses, we could potentially find new ways of dealing with drug-resistant bacteria.