As generative AI rapidly transforms the digital landscape, it brings with it both unprecedented opportunities and formidable challenges—particularly in the realm of cybersecurity. This keynote explores how large language models, synthetic media generators, and autonomous agents are reshaping the threat landscape, enabling novel forms of cyberattacks such as hyper-personalized phishing, deepfake social engineering, and automated vulnerability discovery. At the same time, it examines how defenders can leverage the same technologies to build more resilient systems, from AI-augmented threat detection to real-time incident response and security automation.