The chapter explores how cybersecurity ultimately depends not only on technology but on the biological limits and behaviour of the human brain arguing that every cyber incident, from phishing to system breaches originates in the brain’s decisionmaking circuits, where perception, attention, emotion, and memory shape choices, explaining how different brain regions such as the prefrontal cortex (rational judgment), amygdala (emotional response and fear), anterior cingulate cortex (conflict detection), and striatum (habit formation and reward) influence cybersecurity behaviour. Also, introduces the concept of “decision loop”, describing how the brain processes stimuli (like a suspicious email), interprets sensory data, appraises risk, experiences emotional reactions, and finally acts either safely or mistakenly. Understanding these processes can guide the design of neuroadaptive cybersecurity systems that respond to users’ mental and emotional states in real time adjusting alerts, authentication, and workload based on attention or stress levels. The core theme of the chapter revolves around the fact that “cybersecurity begins in the mind”, defending networks requires defending human cognition itself.