Explore the world of ultrasonic cross-device tracking in this Black Hat conference talk. Delve into the technologies marketers use to track user content across multiple devices for targeted advertising. Learn about the workflow of cross-device tracking, proximity marketing, and Google Cast. Witness demonstrations of attacks like Beacon Trap and Beacon Injection, and understand how data is obtained from providers. Examine the ecosystem surrounding these technologies, including browser extensions and Android permissions. Discover potential solutions and benefits to counter ultrasonic tracking. Gain insights into this cutting-edge marketing tool and its implications for user privacy and security.