This paper studies the problem of resource discovery in unstructured peer-to-peer (P2P) systems. We propose simple policies that make the discovery of resources resilient to coordinated attacks by malicious nodes. We focus on a novel P2P protocol called GUESS [8] that uses a pong cache, a set of currently known nodes, to discover new ones. We describe how to limit pong cache poisoning, a condition in which the ids of malicious nodes appear in the pong caches of good nodes. We propose an ID smearing algorithm (IDSA) and a dynamic network partitioning (DNP) scheme that can be used together to reduce the impact of malicious nodes.