T1127.001

Trusted Developer Utilities Proxy Execution: MSBuild

Description from ATT&CK

Adversaries may use MSBuild to proxy execution of code through a trusted Windows utility. MSBuild.exe (Microsoft Build Engine) is a software build platform used by Visual Studio. It handles XML formatted project files that define requirements for loading and building various platforms and configurations.(Citation: MSDN MSBuild)

Adversaries can abuse MSBuild to proxy execution of malicious code. The inline task capability of MSBuild that was introduced in .NET version 4 allows for C# or Visual Basic code to be inserted into an XML project file.(Citation: MSDN MSBuild)(Citation: Microsoft MSBuild Inline Tasks 2017) MSBuild will compile and execute the inline task. MSBuild.exe is a signed Microsoft binary, so when it is used this way it can execute arbitrary code and bypass application control defenses that are configured to allow MSBuild.exe execution.(Citation: LOLBAS Msbuild)

Atomic Tests

Atomic Test #1 - MSBuild Bypass Using Inline Tasks (C#)

Executes the code in a project file using msbuild.exe. The default C# project example file (T1127.001.csproj) will simply print "Hello From a Code Fragment" and "Hello From a Class." to the screen.

Supported Platforms: windows

auto_generated_guid: 58742c0f-cb01-44cd-a60b-fb26e8871c93

Inputs:

Name	Description	Type	Default Value
filename	Location of the project file	Path	PathToAtomicsFolder\T1127.001\src\T1127.001.csproj
msbuildpath	Default location of MSBuild	Path	C:\Windows\Microsoft.NET\Framework\v4.0.30319
msbuildname	Default name of MSBuild	Path	msbuild.exe

Attack Commands: Run with command_prompt!

#{msbuildpath}\#{msbuildname} #{filename}

Dependencies: Run with powershell!

Description: Project file must exist on disk at specified location (#{filename})

Check Prereq Commands:

if (Test-Path #{filename}) {exit 0} else {exit 1}

Get Prereq Commands:

New-Item -Type Directory (split-path #{filename}) -ErrorAction ignore | Out-Null
Invoke-WebRequest "https://github.com/redcanaryco/atomic-red-team/raw/master/atomics/T1127.001/src/T1127.001.csproj" -OutFile "#{filename}"

Atomic Test #2 - MSBuild Bypass Using Inline Tasks (VB)

Executes the code in a project file using msbuild.exe. The default Visual Basic example file (vb.xml) will simply print "Hello from a Visual Basic inline task!" to the screen.