A method, system, and computer program product containing instructions to provide hardware-based human presence detection. Rather than rely upon software to display a CAPTCHA image, hardware in the form of a sprite engine of a graphics device is used to write a random text string directly to the display device, overlaying the user interface provided by software. Because the sprite engine is isolated from a host operating system for the system, the random text string cannot be captured and processed by software robots running under the host operating system.