Authorization / Active Directory - Unresolved SID



Unresolved SIDs (Security Identifiers) in Active Directory refer to SIDs that cannot be mapped to valid user or group accounts within the domain or forest. SIDs are unique identifiers assigned to security principals (users, groups, and computers) in Windows environments. When an SID is unresolved, it means that Active Directory cannot locate or associate it with a specific security principal.


If an unresolved SID is used in permissions or group memberships, it may inadvertently grant unauthorized access to resources, creating security vulnerabilities. Attackers could potentially exploit these misconfigurations to gain unauthorized access to sensitive data or systems.
Unresolved SIDs can also lead to access control problems. When an unresolved SID is present in permissions, ACLs (Access Control Lists), or group memberships, it can prevent users or applications from accessing resources properly.
Furthermore, unresolved SIDs can disrupt operations, causing errors and failures in applications, file access, or group policy processing.


  • Regular Cleanup: Conduct regular cleanup activities to identify and resolve unresolved SIDs in the Active Directory domain. This can involve using tools like the "Security Identifier (SID) to User (SID2User)" mapping utilities to identify and correct unresolved SIDs.
  • Remove or Correct References: Once unresolved SIDs are identified, take corrective actions to either remove them from permissions, ACLs, or group memberships or replace them with valid SIDs or user/group accounts.
  • Auditing and Monitoring: Implement auditing and monitoring of Active Directory to detect unresolved SID-related issues promptly. Tools and scripts can help automate this process.
  • Training and Awareness: Educate administrators and IT personnel about the importance of proper SID resolution and the risks associated with unresolved SIDs.
  • Proper Decommissioning: When removing users or groups from Active Directory, ensure that they are properly decommissioned, and their references are updated or removed from associated resources.
  • Regular Security Audits: Conduct regular security audits and assessments to identify and remediate permissions and ACL issues related to unresolved SIDs.
  • Documentation: Maintain documentation of security policies, procedures, and configurations to facilitate the tracking and resolution of unresolved SIDs.

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