huntrule

Detect PowerShell COMPRESS OBFUSCATION using ASCII text encoding and stream/compression APIs

Flags PowerShell script blocks that combine ASCII encoding with Deflate/stream handling indicative of obfuscated payload compression.

FreeReviewedSigma · Medium · v2
Product
windows
Category
ps_script
Author
Timur Zinniatullin, oscd.community (SigmaHQ), DRL 1.1
Published
2020-10-18
Updated
2026-07-31
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 script block content consistent with obfuscation routines that use ASCII text encoding and .NET stream and compression objects. Attackers may use these patterns to hide payload logic and make scripts harder to inspect. The detection relies on ScriptBlockText inspection for specific .NET API usage and distinctive string fragments within the script block.

Reporting behind it

Related detections9 linkedT1027 — drag to rearrange
Suspicious PowerShell Invoke-Expression with Replace Obfuscation
Malicious Emmenhtal JavaScript Loader Spawning Encoded PowerShell
Suspicious Python Interpreter Launching Encoded PowerShell via subprocess
Suspicious PS1Bot PowerShell Payload Written to ProgramData (via file_event)
Malicious Non-Interactive Encoded PowerShell Stager (via process_creation)
Suspicious Hidden PowerShell Executing Substring of Dropped File
PowerShell Encoded or Download-Cradle Command Line (via process_creation)
Obfuscated Encoded PowerShell Payload Deployed - PowerShell (via powershell)
Suspicious PowerShell AES Decryption and Reflective Method Invocation in SolarMarker
Detect PowerShell COMPRESS OBFUSCATION using ASCII text encoding and stream/compression APIs
Pivot detection · T1027 · 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.