Windows Security 4697 PowerShell obfuscated content using COMPRESS OBFUSCATION components

ATT&CK techniques

Execution → Defense Evasion

Recon
Resource Dev
Initial Access
Execution
- T1059.001PowerShell
Persistence
Priv Esc
Defense Evasion
- T1027Obfuscated Files or Information
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule flags Windows System Security audit events (EventID 4697) where the service binary name indicates PowerShell use of specific obfuscation-related .NET patterns. Attackers may compress and obfuscate PowerShell script content to hinder inspection and detection. The detection relies on Security log telemetry for EventID 4697 and matching string patterns within the logged ServiceFileName.

Reporting behind it

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Windows Security 4697 PowerShell obfuscated content using COMPRESS OBFUSCATION components

Pivot detection · T1027 · 9 related

Changelog

v2

v2
Candidate ingested via manual entry.2026-07-31
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.

windows-security-detect-obfuscated-powershell-using-compress-compression-stream--7a922f1b

title: Windows Security 4697 PowerShell obfuscated content using COMPRESS OBFUSCATION components
id: 6aea9ee1-e2f0-4af2-9721-7ea9049c5aaa
related:
  - id: 175997c5-803c-4b08-8bb0-70b099f47595
    type: derived
  - id: 7a922f1b-2635-4d6c-91ef-af228b198ad3
    type: derived
status: test
description: This rule flags Windows System Security audit events (EventID 4697) where the service binary name indicates PowerShell use of specific obfuscation-related .NET patterns. Attackers may compress and obfuscate PowerShell script content to hinder inspection and detection. The detection relies on Security log telemetry for EventID 4697 and matching string patterns within the logged ServiceFileName.
references:
  - https://github.com/SigmaHQ/sigma/issues/1009
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/builtin/security/win_security_invoke_obfuscation_via_compress_services_security.yml
author: Timur Zinniatullin, oscd.community, Huntrule Team
date: 2020-10-18
modified: 2022-11-29
tags:
  - attack.stealth
  - attack.t1027
  - attack.execution
  - attack.t1059.001
logsource:
  product: windows
  service: security
  definition: The 'System Security Extension' audit subcategory need to be enabled to log the EID 4697
detection:
  selection:
    EventID: 4697
    ServiceFileName|contains|all:
      - new-object
      - text.encoding]::ascii
      - readtoend
    ServiceFileName|contains:
      - system.io.compression.deflatestream
      - system.io.streamreader
  condition: selection
falsepositives:
  - Unknown
level: medium
license: DRL-1.1

Convert

This rule as a query you can run. Uses no unlock credit.

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