Dozens of viruses — at least — can eavesdrop on host information. Not only did they demonstrate the strategy’s abundance, but they also discovered tools that control it and send signals that tell bacteriophage viruses to flip from chill (lysogeny) into kill (lysis) mode. They showed that in polylysogeny, phages can coexist, their viral DNA or RNA hidden tucked inside the bacterium’s own, replicating right along with the cells. But the infiltrating phages aren’t exactly peaceful; it’s more like mutually assured destruction. And the tenuous detente lasts only until something triggers one or more of the phages to switch into kill mode.