Insiders can engage in malicious activities against organizations such as data theft and sabotage. Prior research on insider threat behavior indicates that once motivated to commit malicious activity, insiders seek opportunity where they can act without being detected. In this research we set up an experiment where we leverage this opportunistic behavior and present participants with messages signaling opportunity for data theft. In the experiment, students were engaged in routine tasks with a bonus based on their performance. While working on their assigned tasks, they were presented with opportunities (probes) to steal data that would increase their payout. Their pre and post probe behavior was observed to test if they engaged in behavior that was deemed suspicious when they received the probe. The goal of the project is to test whether the overclaiming personality trait is a predictor of malicious insider behavior and this was measured through the Over Claiming questionnaire developed by Paulhaus (Paulhaus et al. 2003) The results indicated that over claiming proved to be a strong predictor of malicious insider behavior.