Human-computer interaction (HCI) is the study of how people use, understand, and experience computing systems. It looks at the fit between human behavior and system design: screens, menus, prompts, input devices, error messages, and feedback. In practice, HCI asks not only whether a system works, but whether people can use it safely, quickly, and with confidence.
HCI matters in cyber security because many attacks target the user layer, not just the code layer. Phishing pages imitate trusted interfaces, fake update dialogs pressure users into installing malware, and clickjacking or UI redressing tricks people into approving actions they did not intend. Defenders use HCI principles to design clearer warnings, safer defaults, better authentication flows, and interfaces that reduce mistakes. Good security often depends on making the secure choice the easiest choice.