Adversaries may modify Group Policy Objects (GPOs) to subvert the intended discretionary access controls for a domain, usually with the intention of escalating privileges on the domain. Group policy allows for centralized management of user and computer settings in Active Directory (AD). GPOs are containers for group policy settings made up of files stored within a predicable network path
Like other objects in AD, GPOs have access controls associated with them. By default all user accounts in the domain have permission to read GPOs. It is possible to delegate GPO access control permissions, e.g. write access, to specific users or groups in the domain.
Malicious GPO modifications can be used to implement many other malicious behaviors such as Scheduled Task/Job, Disable or Modify Tools, Ingress Tool Transfer, Create Account, Service Execution, and more. Since GPOs can control so many user and machine settings in the AD environment, there are a great number of potential attacks that can stem from this GPO abuse.
For example, publicly available scripts such as
New-GPOImmediateTask can be leveraged to automate the creation of a malicious Scheduled Task/Job by modifying GPO settings, in this case modifying
<GPO_PATH>\Machine\Preferences\ScheduledTasks\ScheduledTasks.xml. In some cases an adversary might modify specific user rights like SeEnableDelegationPrivilege, set in
<GPO_PATH>\MACHINE\Microsoft\Windows NT\SecEdit\GptTmpl.inf, to achieve a subtle AD backdoor with complete control of the domain because the user account under the adversary's control would then be able to modify GPOs.
|M1018||User Account Management|
|ID||Data Source||Data Component||Detects|
|DS0026||Active Directory||Active Directory Object Creation||
Monitor for newly constructed active directory objects, such as Windows EID 5137.
|Active Directory Object Deletion||
Monitor for unexpected deletion of an active directory object, such as Windows EID 5141.
|Active Directory Object Modification||
Monitor for changes made to AD settings for unexpected modifications to user accounts, such as deletions or potentially malicious changes to user attributes (credentials, status, etc.).
Monitor executed commands and arguments that may modify Group Policy Objects (GPOs) to subvert the intended discretionary access controls for a domain, usually with the intention of escalating privileges on the domain.