In Peer-to-Peer (P2P) networks

peers' features such as heterogeneity

anonymity and autonomy lead to some security problems

such as forging

slandering and collective cheating

which affect the quality of service a lot.A trust model METrust in P2P networks based on the recommendation is proposed

each peer in the network has a unique credibility of recommendation

two trust parameters for updating the credibility of recommendation are introduced

namely updating range and updating strength.The trust model METrust proposes an algorithm to update the credibility of recommendation;a peer selects recommendation peers whose evaluation criteria are similar

evaluation criteria of peers are determined through the AHP method(Analytic Hierarchy Process).Simulations show that

the trust model METrust can identify malicious peers

and improve the quality of service in P2P networks effectively.