A reputation server associates feedback from previous network transactions with an account of a user in a network. A reputation score for the user is calculated based on the feedback to indicate the probability the user will abuse the network. When an online service receives a request to perform a transaction from the user, the online service performs the transaction based on the user's reputation score. Additionally, a server generates a reputation packet including the reputation score for a user for use by an online service when the user requests the online service to perform a transaction. The online service may authenticate the reputation packet with the server and, if the reputation packet is authenticated, the online service performs the transaction based on the user's reputation score.