Definition - What does Friend-To-Friend (F2F) mean?
A friend-to-friend (or F2F) network is a specific form of anonymous peer-to-peer (P2P) network where users only make direct connections with their friends or other users they know. F2F software installed in a system only permits other known users to share files directly to or from that particular system. The software makes use of digital signatures or passwords for authentication.
The term friend-to-friend network was first coined by Dan Bricklin in 2000.
Techopedia explains Friend-To-Friend (F2F)
Because each user is identified with a unique IP address, users can ensure access to their particular friends and prevent the access of other random people within the same ring. In addition, users can also use encryption links to block the exchange of controversial files by removing their friend's public keys from a node. F2F is secure because only the friends of the user are connected with the user's node.
One downside of F2F is that setting up and maintaining an F2F network is difficult because so much of the config is established manually.