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Microsoft Build Engine Started an Unusual Process

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Microsoft Build Engine Started an Unusual Process

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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: new_terms

Rule indices:

winlogbeat-*
logs-endpoint.events.*
logs-windows.*
logs-system.security*

Severity: low

Risk score: 21

Runs every: 5m

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

Maximum alerts per execution: 100

References:

https://blog.talosintelligence.com/2020/02/building-bypass-with-msbuild.html

Tags:

Domain: Endpoint
OS: Windows
Use Case: Threat Detection
Tactic: Defense Evasion
Tactic: Execution
Data Source: Elastic Defend

Version: 210

Rule authors:

Elastic

Rule license: Elastic License v2

Setup

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Setup

If enabling an EQL rule on a non-elastic-agent index (such as beats) for versions <8.2, events will not define event.ingested and default fallback for EQL rules was not added until version 8.2. Hence for this rule to work effectively, users will need to add a custom ingest pipeline to populate event.ingested to @timestamp. For more details on adding a custom ingest pipeline refer - https://www.elastic.co/guide/en/fleet/current/data-streams-pipeline-tutorial.html

Rule query

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host.os.type:windows and event.category:process and event.type:start and process.parent.name:("MSBuild.exe" or "msbuild.exe") and
process.name:("csc.exe" or "iexplore.exe" or "powershell.exe")

Framework: MITRE ATT&CK^TM

Tactic:
- Name: Defense Evasion
- ID: TA0005
- Reference URL: https://attack.mitre.org/tactics/TA0005/
Technique:
- Name: Obfuscated Files or Information
- ID: T1027
- Reference URL: https://attack.mitre.org/techniques/T1027/
Sub-technique:
- Name: Compile After Delivery
- ID: T1027.004
- Reference URL: https://attack.mitre.org/techniques/T1027/004/
Technique:
- Name: Trusted Developer Utilities Proxy Execution
- ID: T1127
- Reference URL: https://attack.mitre.org/techniques/T1127/
Sub-technique:
- Name: MSBuild
- ID: T1127.001
- Reference URL: https://attack.mitre.org/techniques/T1127/001/

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