A superuser is a high-privilege account that can change almost any setting on a device or system. Depending on the platform, this may be called root, administrator, or a similar all-powerful role. A superuser can install software, read protected files, alter security controls, create other accounts, and disable logging or defenses.
In cyber security, superuser access matters because it often turns a limited compromise into full control. Attackers who gain or create a superuser account can persist, cover their tracks, and move from initial access to system ownership. Defenders treat unexpected superuser activity as a serious warning sign, especially on servers, appliances, and identity systems. Good practice includes least-privilege access, separate admin accounts, multi-factor authentication, account auditing, and alerts for new privileged users or privilege escalation.