I've just found this is called Friend-to-friend filesharing: http://en.wikipedia.org/wiki/Friend-to-friend http://en.wikipedia.org/wiki/Friend-to-friend An ext

I've just found this is called Friend-to-friend filesharing: http://en.wikipedia.org/wiki/Friend-to-friend http://en.wikipedia.org/wiki/Friend-to-friend An extract: """A friend-to-friend (or F2F) computer network is a type of peer-to-peer network in which users only make direct connections with people they know. Passwords or digital signatures can be used for authentication. Many F2F networks support indirect anonymous or pseudonymous communication between users who do not know or trust one another. For example, a node in a friend-to-friend overlay can automatically forward a file (or a request for a file) anonymously between two friends, without telling either of them the other's name or IP address. These friends can in turn forward the same file (or request) to their own friends, and so on."""