Home/ATT&CK Technique/MSBuild
ATT&CK Technique

MSBuild

T1127.001 · stealth, execution

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.

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. 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.

Windows
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Atomic Tests

2
Executable Atomic Red Team test cases for exercising this technique in a lab. Copy a command, run it on the listed platform, confirm your detections fire.
command_promptwindowsMSBuild 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. 
#{msbuildpath}\#{msbuildname} "#{filename}"
command_promptwindowsMSBuild 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. 
#{msbuildpath}\#{msbuildname} "#{filename}"
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Mitigations

2
MITRE ATT&CK mitigations - vendor-agnostic guidance for reducing exposure to this technique.
M1038Execution Prevention

Prevent the execution of unauthorized or malicious code on systems by implementing application control, script blocking, and other execution prevention mechanisms. This ensures that only trusted and authorized code is executed, reducing the risk of malware and unauthorized actions.

Application Control
  • Use Case: Use tools like AppLocker or Windows Defender Application Control (WDAC) to create whitelists of authorized applications and block unauthorized ones. On Linux, use tools like SELinux or AppArmor to define mandatory access control policies for application execution.
  • Implementation: Allow only digitally signed or pre-approved applications to execute on servers and endpoints. (e.g., `New-AppLockerPolicy -PolicyType Enforced -FilePath "C:\Policies\AppLocker.
xml"`) Script Blocking
  • Use Case: Use script control mechanisms to block unauthorized execution of scripts, such as PowerShell or JavaScript. Web Browsers: Use browser extensions or settings to block JavaScript execution from untrusted sources.
  • Implementation: Configure PowerShell to enforce Constrained Language Mode for non-administrator users. (e.g.
, Set-ExecutionPolicy AllSigned) Executable Blocking
  • Use Case: Prevent execution of binaries from suspicious locations, such as %TEMP% or %APPDATA% directories.
  • Implementation: Block execution of .exe, .bat, or .ps1 files from user-writable directories.
Dynamic Analysis Prevention
  • Use Case: Use behavior-based execution prevention tools to identify and block malicious activity in real time.
  • Implemenation: Employ EDR solutions that analyze runtime behavior and block suspicious code execution.
M1042Disable or Remove Feature or Program

Disable or remove unnecessary and potentially vulnerable software, features, or services to reduce the attack surface and prevent abuse by adversaries. This involves identifying software or features that are no longer needed or that could be exploited and ensuring they are either removed or properly disabled.

Remove Legacy Software
  • Use Case: Disable or remove older versions of software that no longer receive updates or security patches (e.g., legacy Java, Adobe Flash).
  • Implementation: A company removes Flash Player from all employee systems after it has reached its end-of-life date.
Disable Unused Features
  • Use Case: Turn off unnecessary operating system features like SMBv1, Telnet, or RDP if they are not required.
  • Implementation: Disable SMBv1 in a Windows environment to mitigate vulnerabilities like EternalBlue.
Control Applications Installed by Users
  • Use Case: Prevent users from installing unauthorized software via group policies or other management tools.
  • Implementation: Block user installations of unauthorized file-sharing applications (e.g., BitTorrent clients) in an enterprise environment.
Remove Unnecessary Services
  • Use Case: Identify and disable unnecessary default services running on endpoints, servers, or network devices.
  • Implementation: Disable unused administrative shares (e.g., C$, ADMIN$) on workstations.
Restrict Add-ons and Plugins
  • Use Case: Remove or disable browser plugins and add-ons that are not needed for business purposes.
  • Implementation: Disable Java and ActiveX plugins in web browsers to prevent drive-by attacks.
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Detection Coverage

2/6 layers
Coverage across standard detection surfaces. Rows marked none have no rule of that type mapped. Some are real blind spots worth closing; others are simply not applicable to this technique (e.g. YARA matches malware files, not network behaviour).
Behavioral / log (Sigma) 1
Analytics (MITRE CAR) 1
Runtime / container (Falco) none
File / malware (YARA) none
Network (Suricata/Snort) none
Vuln scan (Nuclei) none
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CAR Analytics

1
MITRE Cyber Analytics Repository - field-tested detection logic for this technique, written as pseudocode/queries you adapt to your own SIEM (Splunk, Sentinel, EQL). Each is a ready starting point for a detection rule, not just a description.
CAR-2020-11-008High coverageMSBuild and msxsl

Trusted developer utilities such as MSBuild may be leveraged to run malicious code with elevated privileges. This analytic looks for any instances of msbuild.exe, which will execute any C# code placed within a given XML document.

and msxsl.exe, which processes xsl transformation specifications for XML files and will execute a variaty of scripting languages contained within the XSL file. Both of these executables are rarely used outside of Visual Studio.

Pseudocode - Pseudocode - msbuild
processes = search Process:Create
target_processes = filter processes where (
  (exe="C:\Program Files (x86)\Microsoft Visual Studio\*\bin\MSBuild.exe" OR exe="C:\Windows\Microsoft.NET\Framework*\msbuild.exe" OR exe="C:\users\*\appdata\roaming\microsoft\msxsl.exe") AND
  image_path!="*Microsoft Visual Studio*")
output target_processes
Splunk - Splunk Search - msbuild
(index=__your_sysmon_index__ EventCode=1) (Image="C:\\Program Files (x86)\\Microsoft Visual Studio\\*\\bin\\MSBuild.exe" OR Image="C:\\Windows\\Microsoft.NET\\Framework*\\msbuild.exe" OR Image="C:\\users\\*\\appdata\\roaming\\microsoft\\msxsl.exe") ParentImage!="*\\Microsoft Visual Studio*")
LogPoint - LogPoint Search - msbuild
norm_id=WindowsSysmon event_id=1 (image IN ["C:\Program Files (x86)\Microsoft Visual Studio\*\bin\MSBuild.exe", "C:\Windows\Microsoft.NET\Framework*\msbuild.exe", "C:\Users\*\appdata\roaming\microsoft\msxsl.exe") -parent_image="*\Microsoft Visual Studio*")
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