On Curbing Virus Propagation.

Let A and B be two sets of computers (not necessarily inanimate). Each computer in A needs to interact once with each computer in B. The order of interaction is not specified. Each computer might be infected with a virus, hence interactions are carried out using interfaces. Conceptually, an interface has two sides and no virus can move from one side of an interface to the other. This allows for possible contagion-free interactions.