Explore the critical balance between privacy and security in the digital age through a 17-minute conference talk by Facebook's Chief Security Officer at Web Summit 2016. Delve into Facebook's mission, the challenges of safety-oriented engineering, and the evolution of authentication methods beyond traditional username and password systems. Examine innovative approaches to account security, including trusted contacts and machine learning, while considering the global implications of these technologies. Gain insights into cutting-edge security tools like OS Query and end-to-end encryption, and understand how tech giants are working to predict and prevent security threats. Learn about Facebook's efforts to empower users through resources like the Safety Center, and reflect on the ongoing challenge of protecting billions of users in an ever-changing digital landscape.