Frauds conducted online are crimes that are and has been increasing in numbers over the last years. Government reports shows that this is the case in Sweden as well as internationally. As of today the Swedish legal systems lacks a definition and categorization approach for online frauds. This thesis aims at developing such definition and a classification scheme that can be used to classify online frauds. Further, this thesis suggests and evaluates a defense mechanism for use in arenas were online frauds are executed. The results bring a definition and classification scheme that has been developed in cooperation with the Swedish police and validated with a judge from a Swedish court. The evaluation of the suggested defense mechanism indicates that our suggested defense mechanism has the potential to make internet users less susceptible to online fraud attacks.