Peer-to-Peer (P2P) computing has become an interesting research topic during recent years. In this paper, we address issue related to analyzing the worm-based attack in P2P systems. Particularly, our technologies include: 1) generic mathematical models for attacker/defender and different P2P systems; 2) practical and effective attack prevention schemes. We find that our proposed defense strategy can efficiently improve the performance of worm detection and system recovery. 1