Baselinesid

Baselinesid is a term used in information security to denote a baseline set of Security Identifiers (SIDs) that identify standard or baseline accounts and principals within an IT environment. It is not a formal standard, but it is commonly referenced in security baselines and auditing practices to help verify that the essential accounts and service identities present on systems conform to an agreed configuration.

A SID is a unique, immutable identifier used by Windows and related systems to represent a security principal, such as a user, group, or computer account. SIDs persist even as user names change, and they participate in access control lists to determine permissions. Typical built-in and service-related SIDs often encountered in baselines include Local System (S-1-5-18), Local Service (S-1-5-19), Network Service (S-1-5-20), and built-in groups such as Administrators (S-1-5-32-544) and Users (S-1-5-32-545).

In practice, Baselinesid can guide configuration management and security auditing by defining the expected set of SIDs on a baseline image or domain. This enables drift detection, such as missing standard accounts, unexpected new accounts, or SIDs introduced by cloning or migration. By anchoring audits to Baselinesid, administrators can assess whether the security posture aligns with the predefined baseline and identify deviations that might indicate misconfigurations or compromise.

Limitations include the fact that SIDs are specific to domains and can change in certain operations (such as domain migrations or reconstitutions). Maintaining an accurate Baselinesid requires careful tracking of domain structure, RID bases, and updates to the baseline when legitimate changes occur.

See also: Security identifier, Windows operating system, Security baselines, Access control.