Provided herein are systems and methods for classifying content to prevent data breach or exfiltration. An entity engine may receive content for classification into a content type for preventing data breach or exfiltration. The entity engine may determine that secondary data, defined by an operand of an entity definition, is present in the content. Each entity definition may correspond to one content type and may include a Boolean expression of operands. Each operand may include a matching element to be used for matching against content undergoing classification into one of the content types, upon secondary data defined by the operand being present in the content. The entity engine may classify the content into a content type of the content types, corresponding to the entity definition, based on matching the matching element of the operand to the content, and matching other operands of the entity definition to the content.