Microsoft Build Engine Started an Unusual Processedit

An instance of MSBuild, the Microsoft Build Engine, started a PowerShell script or the Visual C# Command Line Compiler. This technique is sometimes used to deploy a malicious payload using the Build Engine.

Rule type: query

Rule indices:

  • winlogbeat-*
  • logs-endpoint.events.*

Severity: low

Risk score: 21

Runs every: 5 minutes

Searches indices from: now-9m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100

References:

Tags:

  • Elastic
  • Windows

Version: 3 (version history)

Added (Elastic Stack release): 7.7.0

Last modified (Elastic Stack release): 7.9.1

Rule authors: Elastic

Rule license: Elastic License

Potential false positivesedit

The Build Engine is commonly used by Windows developers but use by non-engineers is unusual. If a build system triggers this rule it can be exempted by process, user or host name.

Rule queryedit

event.category:process and event.type:(start or process_started) and
process.parent.name:MSBuild.exe and process.name:(csc.exe or
iexplore.exe or powershell.exe)

Threat mappingedit

Framework: MITRE ATT&CKTM

Rule version historyedit

Version 3 (7.9.1 release)
  • Formatting only
Version 2 (7.9.0 release)
  • Updated query, changed from:

    process.parent.name:MSBuild.exe and process.name:(csc.exe or
    iexplore.exe or powershell.exe)