huntrule

Windows PowerShell: Base64 Encoded Reflective .NET Assembly Load

Flags PowerShell command lines containing Base64 fragments consistent with reflective .NET Assembly.Load usage.

FreeReviewedSigma · High · v1
Product
windows
Category
process_creation
Author
Christian Burkard (Nextron Systems), pH-T (Nextron Systems) (SigmaHQ), DRL 1.1
Published
2022-03-01
Updated
2026-07-30
AnalysisDetection

ATT&CK techniques

Execution → Defense Evasion

  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 identifies PowerShell process command lines containing Base64-encoded content that corresponds to reflective .NET assembly loading patterns. Attackers commonly use encoded payloads to reduce detection and stage in-memory execution without writing readable artifacts to disk. The detection relies on Windows process creation telemetry and substring matches on specific Base64 fragments representing calls like Reflection.Assembly.Load.

Reporting behind it

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Windows PowerShell: Base64 Encoded Reflective .NET Assembly Load
Pivot detection · T1059.001 · 9 related

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