huntrule

PowerShell downgrade indicators via EngineVersion=2. and HostVersion !=2. (Windows)

Detects PowerShell version mismatches that may indicate a downgrade attempt using EngineVersion vs HostVersion telemetry.

FreeReviewedSigma · Medium · v2
Product
windows
Category
ps_classic_start
Author
Florian Roth (Nextron Systems), Lee Holmes (idea), Harish Segar (improvements) (SigmaHQ), DRL 1.1
Published
2017-03-22
Updated
2026-07-31
AnalysisDetection

ATT&CK techniques

Execution

  1. Recon

  2. Resource Dev

  3. Initial Access

  4. Execution

  5. Persistence

  6. Priv Esc

  7. Defense Evasion

  8. Cred Access

  9. Discovery

  10. Lateral Movement

  11. Collection

  12. C2

  13. Exfiltration

  14. Impact

What it detects

This rule flags PowerShell activity where the reported EngineVersion contains "EngineVersion=2." but the related HostVersion does not contain "HostVersion=2." PowerShell downgrade attacks matter because they can coerce a victim into using a different engine/feature set than the host expects. The detection relies on string matches within PowerShell classic start telemetry fields for EngineVersion and HostVersion.

Reporting behind it

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Suspicious In-Memory PowerShell Execution from Web Server via Automation Assembly (via image_load)
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PowerShell downgrade indicators via EngineVersion=2. and HostVersion !=2. (Windows)
Pivot detection · T1059.001 · 9 related

Changelog

v2
  1. v2
    Candidate ingested via manual entry.2026-07-31
  2. v1
    No changelog recorded for this version.2026-07-30

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.