Daswani points out that anyone can join a peer-to-peer network, so it cannot be run on trust. Instead, the researchers gave each node a set of simple rules to follow when processing requests from other peers. They found that when requests from ordinary nodes were treated in a different way to requests from supernodes the damage caused by a flooding attack was dramatically reduced.During a flood attack, a malicious P2P client hammers other nodes with fake file requests, clogging the network as a result. It's like a Denial-of-Service attack for P2P networks, and something that proposed laws could let the RIAA unleash at will.
Even if the RIAA doesn't win the right to flood P2P nodes, I imagine that malicious P2P attacks will only become more popular as the networks themselves become more mainstream. Hopefully, we'll see more of this kind of research in the future.