1. A computerized method of a processor of a computing device for authenticating a user based on a network-wide reputation for the user, said user having a user account associated therewith for accessing one or more online services of the network, said method comprising: associating, by the processor, reputation feedback with the user account, said reputation feedback being based on one or more past transactions between the user and at least one of the online services of the network, said reputation feedback indicating whether or not any of the past transactions constitutes a misuse of the network; calculating, by the processor, a reputation score for the user based on the reputation feedback associated with the user account for the past transactions, said reputation score indicating a likelihood of misuse of the network; generating, by the processor, a reputation packet including the user's reputation score; authenticating, by the processor, the reputation packet in response to a request from the user to perform a present transaction with at least one of the online services of the network, said request to perform the present transaction and said authenticated reputation packet being sent to the at least one of the online services; receiving, by the processor, from the at least one of the online services, a reputation feedback based on a solved at least one of a computational proof and a human interactive proof, the proof being solved by the user in response to a request from the at least one of the online services determining the user's reputation score is not sufficient to grant the user's request to perform the present transaction; and adjusting, by the processor, the user's reputation score based on the received feedback.