A detection device for detecting a fraud behavior of a customer at a point-of-sale (POS) terminal in a store, including a first interface circuit configured to receive a first image of the customer from a camera, a second interface circuit configured to receive a second image that is displayed on the POS terminal, and a processor configured to acquire one or more first images via the first interface circuit and determine one or more behaviors of the customer based on the acquired first images, acquire one or more second images via the second interface circuit and determine, based on the acquired second images, one or more operations that have been made by the customer on the POS terminal, and determine that one of the behaviors is fraudulent based on one or more of the operations that have been made by the customer before said one of the behaviors.