A computer-implemented technique provides security to an enterprise. The technique involves receiving, by processing circuitry, personal information belonging to users of the enterprise. The technique further involves providing, by the processing circuitry, lists of user identifiers based on user relationships defined by the personal information. The lists of user identifiers respectively identify clusters of users of the enterprise. The technique further involves electronically imposing, by the processing circuitry, security classes on the clusters of users of the enterprise based on the lists of user identifiers. Along these lines, such classification can be used for risk assessment (e.g., authentication), alert filtering (e.g., filtering false alarms), and permission/privilege monitoring and/or assignment, among others.