A wearable computer determines unnatural movements of a head-mounted display (HMD) and triggers a locking mechanism. In one embodiment, the wearable computer receives movement data from one or more sensors and determines that the movement of the HMD is unnatural. In one embodiment, the wearable computer receives movement data from one or more sensors and determines that the HMD is being worn by an unauthorized user. In response to determining an unnatural movement and/or an unauthorized user wearing the HMD, the wearable computer triggers a locking mechanism, which can beneficially provide security measures for the wearable computer.