SID (Security Identifier)

A Security Identifier (SID) is a unique string of characters assigned to a user, group, or system resource in Windows environments. It serves as a global, unique identifier that the operating system uses to manage permissions and access control. Instead of relying on names, which can change, Windows uses SIDs to reliably recognize and verify the identity of each entity. This ensures consistent security management across the system, even if user or group names are renamed. In essence, the SID is like a fingerprint that the system uses to identify and enforce security policies for users and resources.