Abstract: Due to the open nature of P2P system exposes them to malicious activity. P2P system means computer in the system can act as both client and server. In a P2P network, the peers are computer systems which are connected to each other via the internet. Files can be shared directly between systems on the network without the need of a central server. Building trust relationships among peers can decrease the attacks of malicious peers. A good peer uploads reliable files and gives fair recommendations. A peer’s trustworthiness is evaluated by considering provided services and given recommendations with service and recommendation contexts .A malicious peer performs both service and recommendation-based attacks. Uploading a virus infected (or) an inauthentic file is a service based attack. Self-Organizing Trust Model (SORT) detects the service based attack and recommendation based attack.