Windows PowerShell: Detect Set-Alias/New-Alias Usage in Script Block Logging

Alerts on PowerShell scripts that create aliases via Set-Alias/New-Alias, a common obfuscation technique, using ScriptBlockText logging.

FreeReviewedSigma · Low · v4

Product: windows
Category: ps_script
Author: frack113 (SigmaHQ), DRL 1.1
Published: 2023-01-08
Updated: 2026-09-24

Analysis Detection

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 contains Set-Alias or New-Alias, which attackers can use to obscure command intent by creating alternate command names. It relies on Script Block Logging telemetry, matching on ScriptBlockText strings to identify alias creation activity and excluding specific known benign alias mappings. The detection is intended to surface potentially stealthy PowerShell execution patterns.

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 Encoded PowerShell Using Base64 Stream Decompression Routines (via process_creation)

Suspicious PowerShell In-Memory Execution with AES Decryption

Suspicious Encoded PowerShell Command Execution

Suspicious PEAKLIGHT Memory-Only PowerShell Downloader Flags (via process_creation)

Obfuscated PowerShell Script: Indirect Cmdlet Execution via ExportedCommands Array Index

Windows PowerShell: Detect Set-Alias/New-Alias Usage in Script Block Logging

Pivot detection · T1027 · 9 related

Changelog

v4
Candidate ingested via manual entry.2026-09-24
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.

powershell-alias-cmdlets-set-alias-new-alias-in-script-block-logging-96cd126d

title: "Windows PowerShell: Detect Set-Alias/New-Alias Usage in Script Block Logging"
id: 1d3f833a-a48b-4fc5-aa76-728498df1000
related:
  - id: e8314f79-564d-4f79-bc13-fbc0bf2660d8
    type: derived
  - id: 96cd126d-f970-49c4-848a-da3a09f55c55
    type: derived
status: test
description: This rule flags PowerShell script content that contains Set-Alias or New-Alias, which attackers can use to obscure command intent by creating alternate command names. It relies on Script Block Logging telemetry, matching on ScriptBlockText strings to identify alias creation activity and excluding specific known benign alias mappings. The detection is intended to surface potentially stealthy PowerShell execution patterns.
references:
  - https://github.com/1337Rin/Swag-PSO
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/powershell/powershell_script/posh_ps_susp_set_alias.yml
author: frack113, Huntrule Team
date: 2023-01-08
modified: 2026-09-17
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:
      - "Set-Alias "
      - "New-Alias "
  filter_main_cim:
    ScriptBlockText:
      - Set-Alias -Name ncms -Value New-CimSession -Option ReadOnly, AllScope -ErrorAction SilentlyContinue
      - Set-Alias -Name gcls -Value Get-CimClass -Option ReadOnly, AllScope -ErrorAction SilentlyContinue
      - Set-Alias -Name ncso -Value New-CimSessionOption -Option ReadOnly, AllScope -ErrorAction SilentlyContinue
      - Set-Alias -Name gcms -Value Get-CimSession -Option ReadOnly, AllScope -ErrorAction SilentlyContinue
      - Set-Alias -Name rcms -Value Remove-cimSession -Option ReadOnly, AllScope -ErrorAction SilentlyContinue
      - Set-Alias -Name rcie -Value Register-CimIndicationEvent -Option ReadOnly, AllScope -ErrorAction SilentlyContinue
      - Set-Alias -Name gcai -Value Get-CimAssociatedInstance -Option ReadOnly, AllScope -ErrorAction SilentlyContinue
      - Set-Alias -Name gcim -Value Get-CimInstance -Option ReadOnly, AllScope -ErrorAction SilentlyContinue
      - Set-Alias -Name scim -Value Set-CimInstance -Option ReadOnly, AllScope -ErrorAction SilentlyContinue
      - Set-Alias -Name ncim -Value New-CimInstance -Option ReadOnly, AllScope -ErrorAction SilentlyContinue
      - Set-Alias -Name ncim -Value New-CimInstance  -Option ReadOnly, AllScope -ErrorAction SilentlyContinue
      - Set-Alias -Name rcim -Value Remove-cimInstance -Option ReadOnly, AllScope -ErrorAction SilentlyContinue
      - Set-Alias -Name icim -Value Invoke-CimMethod -Option ReadOnly, AllScope -ErrorAction SilentlyContinue
  condition: selection and not 1 of filter_main_*
falsepositives:
  - Unknown
level: low
license: DRL-1.1

Convert

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

SplunkSPL