huntrule

Windows Process Creation: Base64-Obfuscated .NET Reflection Assembly Load Call

Alerts on command lines containing Base64-encoded obfuscation for .NET reflection assembly load calls.

FreeReviewedSigma · High · v1
Product
windows
Category
process_creation
Author
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 flags Windows process creation events whose command line contains specific Base64-encoded strings that reconstruct an obfuscated .NET reflection.assembly load keyword. Attackers may use encoding and string concatenation to evade simple keyword matching and to conceal dynamic assembly loading behavior. It relies on process_creation telemetry with access to the full command line text.

Reporting behind it

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Windows Process Creation: Base64-Obfuscated .NET Reflection Assembly Load Call
Pivot detection · T1027 · 9 related

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