In this paper, we present insights generated by modeling the emergence of insider threat vulnerabilities in organizations. In our model, we integrate concepts from social judgment theory, signal detection theory, and the cognitive psychology of memory and belief formation. With this model, we investigate the emergence of vulnerabilities (especially that are insider-driven) in complex systems characterized by high levels of feedback complexity, multiple actors, and the presence of uncertainty in the judgment and decision processes. We use the system dynamics method of computer simulation to investigate the consequences caused by changes to the model's assumptions. We find that the emergence of vulnerability can be an endogenous process and that leverage points to reduce this vulnerability involve improvement in information acquisition, information management, and the training of personnel in judgment and decision-making techniques.