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

Related detections9 linkedT1027 — drag to rearrange
Malicious FIN7 Powertrash Loader Execution via Obfuscated PowerShell (via process_creation)
Suspicious XOR Obfuscated PowerShell from ClickFix Distribution
Suspicious PowerShell Executing Code from Environment Variable (via process_creation)
Suspicious In-Memory Runspace Execution via PowerShell Script Block
Suspicious PowerShell Reflective Assembly Load With Registry Property Read via Script Block (via ps_script)
Suspicious Encoded PowerShell Using Base64 Stream Decompression Routines (via process_creation)
Suspicious In-Memory .NET Assembly Load via PowerShell Base64 Payload (via process_creation)
Suspicious PowerShell In-Memory Execution with AES Decryption
Suspicious Encoded PowerShell Command Execution
Windows PowerShell: Base64 Encoded Reflective .NET Assembly Load
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.