Misconfigured WriteOwner permissions in Active Directory can enable attackers to take ownership of critical objects, bypass security controls, and escalate privileges. This technical analysis explores detection methods and defensive strategies for security teams to protect against DACL-based attacks.
Understanding WriteOwner Risks in Active Directory
Active Directory’s Discretionary Access Control Lists (DACLs) contain critical permissions that govern object access. The WriteOwner right (ADS_RIGHT_WRITE_OWNER) presents particular risk, as documented in The Hacker Recipes and Hacking Articles. When improperly assigned, this permission allows security principals to:
- Reassign ownership of users, groups, or computers
- Gain implicit WriteDacl privileges through ownership
- Modify security descriptors regardless of existing DACL restrictions
Detection and Investigation Techniques
Security teams should implement these detection strategies to identify potential WriteOwner abuse:
BloodHound Queries
The following Cypher query helps identify dangerous WriteOwner relationships, particularly targeting privileged groups:
MATCH (n)-[r:WriteOwner]->(m)
WHERE m.objectid ENDS WITH "-512"
RETURN rSIEM Monitoring
Windows Event ID 4662 (object owner changes) provides critical audit data. Security teams should create alerts for owner modifications on sensitive objects like Domain Admins (RID 512) and Enterprise Admins.
Defensive Recommendations
Based on Microsoft’s tiered administration model and Lares Labs research, organizations should:
Permission Hardening
- Apply DenyWriteOwner permissions to Tier 0 assets via Group Policy
- Implement quarterly ACL reviews using tools like PingCastle
- Restrict ownership rights to designated admin accounts only
Monitoring Enhancements
- Configure alerts for owner changes on privileged groups
- Integrate BloodHound defensive queries into security operations
- Monitor for subsequent WriteDacl modifications after ownership changes
Operational Impact Analysis
This vulnerability affects different security functions:
| Team | Considerations |
|---|---|
| Red Teams | Validates privilege escalation paths during assessments |
| Blue Teams | Requires enhanced monitoring of object ownership changes |
| Admins | Necessitates regular ACL reviews and permission audits |
Conclusion
WriteOwner abuse remains a significant Active Directory threat due to inheritance of ownership privileges. While tools like BloodHound improve visibility, organizations must implement proactive ACL hardening and monitoring to protect Tier 0 assets from DACL-based attacks.
