This eBook provides a strategic roadmap for securing autonomous AI systems, addressing the critical shift from protecting static content to managing the risks of independent decision-making and execution. It introduces the A2AS framework and BASIC security model to offer actionable guidance on runtime enforcement, prompt firewalls and threat modeling for agentic environments. Designed for security architects and leaders, the guide bridges the gap between traditional cybersecurity and the emerging challenges of AI collaborators operating without continuous human oversight.