In one embodiment, a peer-to-peer computer network has a multilevel tree structure that includes a plurality of computers. Each computer belonging to the network is assigned to a level such that it can receive a message from an upstream computer and push the message to a downstream computer. The message, which may be a pattern file of an antivirus program, may be rapidly propagated to available computers belonging to the network by pushing the message from a pattern file server to computers on a top level of the network, from computers on the top level of the network to computers on a lower level, and so on.