A liveness check is a security process used in biometric authentication systems to verify that the biometric sample, such as a selfie or fingerprint, is being provided by a live person rather than a static image, video, or artificial replica. This check helps prevent spoofing attacks, where attackers try to bypass security by presenting photos, masks, or recordings. Liveness detection can involve analyzing subtle movements, changes in facial expressions, or responses to prompts, ensuring the authenticity of the biometric input. By confirming that the user is physically present, liveness checks add an essential layer of protection to digital identity verification and access control systems.