PowerShell script alias obfuscation via -Value (-join(...))

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 PowerShell script content that includes both alias creation keywords (New-Alias/Set-Alias) and an obfuscated value built with the -Value (-join(...)) pattern. Attackers may use string joining to conceal alias targets within scripts and reduce straightforward inspection. It relies on Script Block Text containing the required substrings, such as "-Alias" and " -Value (-join(".

Reporting behind it

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PowerShell script alias obfuscation via -Value (-join(...))

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-powershell-alias-obfuscation-via-value-join-in-script-blocks-e8314f79

title: PowerShell script alias obfuscation via -Value (-join(...))
id: c239e4f9-f87f-467e-b86c-2f05d8f90138
related:
  - id: 96cd126d-f970-49c4-848a-da3a09f55c55
    type: derived
  - id: e8314f79-564d-4f79-bc13-fbc0bf2660d8
    type: derived
status: test
description: This rule flags PowerShell script content that includes both alias creation keywords (New-Alias/Set-Alias) and an obfuscated value built with the -Value (-join(...)) pattern. Attackers may use string joining to conceal alias targets within scripts and reduce straightforward inspection. It relies on Script Block Text containing the required substrings, such as "-Alias" and " -Value (-join(".
references:
  - Internal Research
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/powershell/powershell_script/posh_ps_susp_alias_obfscuation.yml
author: Nasreddine Bencherchali (Nextron Systems), Huntrule Team
date: 2023-01-09
tags:
  - attack.execution
  - attack.stealth
  - attack.t1027
  - attack.t1059.001
logsource:
  product: windows
  category: ps_script
  definition: "Requirements: Script Block Logging must be enabled"
detection:
  selection:
    ScriptBlockText|contains|all:
      - -Alias
      - " -Value (-join("
  condition: selection
falsepositives:
  - Unknown
level: low
license: DRL-1.1

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

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