A method and system for generating a behavior profile for a new entity to be added to a behavior-monitored system include receiving feature data of a new entity and feature data of a plurality of pre-existing entities from at least one data source. The plurality of pre-existing entities are associated with a plurality of pre-existing behavior profiles. A doppelganger behavior profile is determined for the new entity based at least partially on the feature data of the new entity and the feature data of the plurality of pre-existing entities, and the doppelganger behavior profile is assigned to the new entity. A target action is implemented with respect to the new entity based at least partially on the doppelganger behavior profile assigned to the new entity.