Techniques
Sample rules
Windows AD AdminSDHolder ACL Modified
- source: splunk
- technicques:
- T1546
Description
The following analytic identifies the modification of the Access Control List for the AdminSDHolder object within a Windows domain. Specifically, the detection triggers on the addition of a new rule to the existing ACL. AdminSDHolder is an object located in the System Partition in Active Directory and is used as a security template for objects that are members of certain privileged groups. Objects in these groups are enumerated and any objects with security descriptors that dont match the AdminSDHolder ACL are flagged for updating. The Security Descriptor propagator (SDProp) process runs every 60 minutes on the PDC Emulator and re-stamps the object Access Control List (ACL) with the security permissions set on the AdminSDHolder. An adversary who has obtained privileged access to a Windows Domain may modify the AdminSDHolder ACL to establish persistence and allow an unprivileged user to take control of a domain.
Detection logic
`wineventlog_security` EventCode=5136 AttributeLDAPDisplayName=nTSecurityDescriptor OperationType="%%14674" ObjectDN="CN=AdminSDHolder,CN=System*"
| rex field=AttributeValue max_match=10000 "A;;CCDCLCSWRPWPDTLOCRSDRCWDWO;;;(?P<added_user_sid>S-1-[0-59]-\d{2}-\d{8,10}-\d{8,10}-\d{8,10}-[1-9]\d{3})\)"
| stats values(added_user_sid) by _time, Computer, SubjectUserName, ObjectDN
| `windows_ad_adminsdholder_acl_modified_filter`