A directory service is a centralized system that stores identity and account information for users, devices, and sometimes groups or roles. Common examples include enterprise directories that hold usernames, email addresses, login attributes, group memberships, and access flags used by business applications.
In cyber security, directory services matter because they often control authentication and authorization. If an attacker compromises a directory, they may be able to reset passwords, escalate privileges, or move laterally across connected systems. Defenders rely on directory services for single sign-on, access control, auditing, and account lifecycle management. They also monitor for weak permissions, stale accounts, and suspicious changes to identity records. Because many tools trust the directory as a source of truth, protecting it is essential: if identity data is inaccurate or exposed, the entire access model can become unsafe.