A polygraph machine, commonly referred to as a lie detector, is a device used to measure and record physiological indicators such as heart rate, blood pressure, respiration, and skin conductivity while a person answers questions. The underlying theory is that deceptive answers will produce physiological responses that can be differentiated from those associated with truthful answers. In cybersecurity and digital forensics, polygraph machines are rarely used directly, but the concept of monitoring physiological or behavioral cues to detect deception has inspired the development of advanced user authentication and fraud detection systems. The reliability and admissibility of polygraph results remain controversial in legal and professional contexts.