Abstract: Malicious activity can be detected and prevented in real-time or otherwise. For example, a system of the present disclosure can receive a request from a user to obtain access to an entity, determine data objects based on the request, and access data-object network definitions corresponding to the determined data objects. The system can also receive a profile for the user indicating behavioral information relating to the user. The system can then determine a likelihood that the request is associated with malicious activity based on (i) the data objects, (ii) the profile, and (iii) the data-object network definitions. The system can allow or deny the user access to the entity based on the likelihood that the request is associated with malicious activity.