This study examines perceptions of human trustworthiness as a key component in countering insider threats. The term insider threat refers to situations where a critical member of an organization behaves against the interests of the organization, in an illegal and/or unethical manner. Identifying how an individual’s behavior varies over time - and how anomalous behavior can be detected - are important elements in the preventive control of insider threat behaviors in securing cyber infrastructure. Using online team-based game-playing, this study seeks to re-create realistic insider threat situations in which human “sensors” can observe changes in a target’s behavior. The intellectual merit of this socio-technical study lies in its capability to tackle complex insider threat problems by adopting a social psychological theory on predicting human trustworthiness in a virtual collaborative environment. The study contributes to a theoretical framework of trustworthiness attribution, and gameplaying methodology to predict the occurrence of malfeasance.