Detect Trusted Developer Utilities Proxy Execution in Microsoft Sentinel
Adversaries may take advantage of trusted developer utilities to proxy execution of malicious payloads. Utilities used for software development tasks such as MSBuild, csc.exe, vbc.exe, WinDbg, cdb.exe, tracker.exe, dnx.exe, and rcsi.exe are typically signed with legitimate Microsoft certificates, allowing them to execute code and bypass application control solutions. These utilities can compile and execute inline C#, VB.NET, or native shellcode embedded in project files, scripts, or command-line arguments, effectively masquerading malicious execution as legitimate developer activity. Adversaries also leverage these tools to bypass Smart App Control by abusing the OS trust model for signed binaries that support arbitrary code execution.
MITRE ATT&CK
- Tactic
- Defense Evasion
- Canonical reference
- https://attack.mitre.org/techniques/T1127/
KQL Detection Query
let TrustedDevUtils = dynamic([
"msbuild.exe", "csc.exe", "vbc.exe", "jsc.exe",
"dnx.exe", "rcsi.exe", "tracker.exe",
"cdb.exe", "windbg.exe", "kd.exe", "ntsd.exe",
"msdeploy.exe", "xwizard.exe", "mshta.exe"
]);
let SuspiciousParents = dynamic([
"winword.exe", "excel.exe", "powerpnt.exe", "outlook.exe",
"msedge.exe", "chrome.exe", "firefox.exe", "iexplore.exe",
"wscript.exe", "cscript.exe", "mshta.exe", "cmd.exe",
"powershell.exe", "pwsh.exe"
]);
let SuspiciousPaths = dynamic([
"\\Temp\\", "\\AppData\\Local\\Temp\\", "\\AppData\\Roaming\\",
"\\ProgramData\\", "\\Users\\Public\\", "\\Downloads\\"
]);
DeviceProcessEvents
| where Timestamp > ago(24h)
| where FileName in~ (TrustedDevUtils)
| extend LaunchedBySuspiciousParent = InitiatingProcessFileName in~ (SuspiciousParents)
| extend FileFromSuspiciousPath = ProcessCommandLine has_any (SuspiciousPaths)
| extend MSBuildInlineTask = FileName =~ "msbuild.exe" and ProcessCommandLine has_any (".csproj", ".proj", ".xml", ".targets", ".tasks")
| extend CompilerFromTemp = FileName in~ ("csc.exe", "vbc.exe", "jsc.exe") and ProcessCommandLine has_any (SuspiciousPaths)
| extend DebuggerShellcode = FileName in~ ("cdb.exe", "windbg.exe", "ntsd.exe", "kd.exe") and ProcessCommandLine has_any ("-pd", "-pv", "-cf", "-c ")
| extend TrackerExec = FileName =~ "tracker.exe" and ProcessCommandLine has_any ("/d3", "/dumpstartuplogging", ".dll", ".exe")
| extend RareUtility = FileName in~ ("dnx.exe", "rcsi.exe")
| where LaunchedBySuspiciousParent
or FileFromSuspiciousPath
or CompilerFromTemp
or DebuggerShellcode
or TrackerExec
or RareUtility
| project Timestamp, DeviceName, AccountName, FileName, ProcessCommandLine,
InitiatingProcessFileName, InitiatingProcessCommandLine,
FolderPath,
LaunchedBySuspiciousParent, FileFromSuspiciousPath, MSBuildInlineTask,
CompilerFromTemp, DebuggerShellcode, TrackerExec, RareUtility
| sort by Timestamp descDetects execution of trusted developer utilities (MSBuild, csc.exe, vbc.exe, WinDbg, cdb.exe, tracker.exe, dnx.exe, rcsi.exe) in suspicious contexts using Microsoft Defender for Endpoint DeviceProcessEvents. Identifies execution spawned by Office applications, browsers, or script interpreters; compiler or build tool invocations referencing temp/user paths; debugger-based shellcode execution via -cf/-c flags; and rare utilities with no legitimate enterprise footprint. Each detection branch is flagged independently to help analysts prioritize.
Data Sources
Required Tables
False Positives & Tuning
- Developer workstations where engineers legitimately invoke MSBuild, csc.exe, or vbc.exe from scripts and IDE terminal sessions
- CI/CD agents (Azure DevOps, Jenkins, TeamCity) that build .NET code using MSBuild or csc.exe — often running as SYSTEM or a service account from non-standard working directories
- IT automation frameworks that compile helper DLLs on-demand from scripts (e.g., some Ansible Windows modules use inline C# via csc.exe)
- Debugging and crash analysis workflows where WinDbg or cdb.exe is legitimately invoked by developers or support engineers
- Visual Studio and Roslyn toolchain processes that compile code from user profile temp directories during incremental builds
Other platforms for T1127
Testing Methodology
Validate this detection against 4 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1MSBuild Inline Task Execution via Malicious Project File
Expected signal: Sysmon Event ID 1: Process Create for MSBuild.exe with CommandLine referencing %TEMP%\malicious.csproj. Sysmon Event ID 11: File Create for %TEMP%\malicious.csproj. Sysmon Event ID 1 child: cmd.exe spawned by MSBuild.exe with /c whoami argument. Sysmon Event ID 11: File Create for %TEMP%\msbuild-test.txt. Security Event ID 4688 for both MSBuild.exe and cmd.exe if command line auditing is enabled.
- Test 2On-the-Fly C# Compilation and Execution via csc.exe
Expected signal: Sysmon Event ID 11: File Create for %TEMP%\df00tech_test.cs. Sysmon Event ID 1: Process Create for csc.exe with CommandLine referencing %TEMP% source and output paths. Sysmon Event ID 11: File Create for %TEMP%\df00tech_test.exe and %TEMP%\df00tech_test.pdb. Sysmon Event ID 1: Process Create for %TEMP%\df00tech_test.exe (unsigned binary from temp path). AmCache will record the new executable's first execution.
- Test 3Shellcode Execution via CDB.exe Debugger with Command Script Flag
Expected signal: Sysmon Event ID 1: Process Create for cdb.exe with CommandLine containing -c, -pv, and -pd flags. Sysmon Event ID 1: Process Create for notepad.exe spawned by cdb.exe. Security Event ID 4688 for cdb.exe if command line auditing enabled. The -c flag content (.echo) will appear in the command line.
- Test 4Tracker.exe Proxy Execution via /d3 Logging Flag
Expected signal: Sysmon Event ID 1: Process Create for Tracker.exe with CommandLine containing /d3 and referencing a DLL. Sysmon Event ID 7: Image Load events for shell32.dll under the Tracker.exe process context. Sysmon Event ID 1: Process Create for whoami.exe as a child of Tracker.exe. Security Event ID 4688 for Tracker.exe and whoami.exe.
References (12)
- https://attack.mitre.org/techniques/T1127/
- https://lolbas-project.github.io/lolbas/OtherMSBinaries/Tracker/
- https://enigma0x3.net/2016/11/17/bypassing-application-whitelisting-by-using-dnx-exe/
- https://enigma0x3.net/2016/11/21/bypassing-application-whitelisting-by-using-rcsi-exe/
- https://web.archive.org/web/20160816135945/http://www.exploit-monday.com/2016/08/windbg-cdb-shellcode-runner.html
- https://www.elastic.co/security-labs/dismantling-smart-app-control
- https://support.microsoft.com/en-us/windows/smart-app-control-frequently-asked-questions-285ea03d-fa88-4d56-882e-6698afdb7003
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1127/T1127.md
- https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_msbuild_susp_parent.yml
- https://learn.microsoft.com/en-us/visualstudio/msbuild/msbuild-inline-tasks
- https://learn.microsoft.com/en-us/windows-hardware/drivers/debugger/cdb-command-line-options
- https://lolbas-project.github.io/lolbas/OtherMSBinaries/Msbuild/
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