Windows PowerShell Base64 Encoded Commands Containing Invoke- ( -e )

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 identifies process executions of PowerShell (powershell.exe or pwsh.exe) where the command line includes the encoded command flag (-e) and the encoded payload matches Base64 fragments consistent with an 'Invoke-' call. Attackers frequently use Base64-encoded PowerShell to obscure script content and reduce casual inspection. The detection relies on process creation telemetry including the executable path and the raw command-line string.

Reporting behind it

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Windows PowerShell Base64 Encoded Commands Containing Invoke- ( -e )

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.

windows-powershell-base64-encoded-commands-containing-invoke-e-6385697e

title: Windows PowerShell Base64 Encoded Commands Containing Invoke- ( -e )
id: 0d4d59a8-d8fe-4c56-85b5-daaddfeb4b11
related:
  - id: fd6e2919-3936-40c9-99db-0aa922c356f7
    type: obsolete
  - id: 6385697e-9f1b-40bd-8817-f4a91f40508e
    type: derived
status: test
description: This rule identifies process executions of PowerShell (powershell.exe or pwsh.exe) where the command line includes the encoded command flag (-e) and the encoded payload matches Base64 fragments consistent with an 'Invoke-' call. Attackers frequently use Base64-encoded PowerShell to obscure script content and reduce casual inspection. The detection relies on process creation telemetry including the executable path and the raw command-line string.
references:
  - https://thedfirreport.com/2022/05/09/seo-poisoning-a-gootloader-story/
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_powershell_base64_invoke.yml
author: pH-T (Nextron Systems), Harjot Singh, @cyb3rjy0t, Huntrule Team
date: 2022-05-20
modified: 2023-04-06
tags:
  - attack.execution
  - attack.stealth
  - attack.t1059.001
  - attack.t1027
logsource:
  category: process_creation
  product: windows
detection:
  selection_img:
    - Image|endswith:
        - \powershell.exe
        - \pwsh.exe
    - OriginalFileName:
        - PowerShell.EXE
        - pwsh.dll
  selection_cli_enc:
    CommandLine|contains: " -e"
  selection_cli_invoke:
    CommandLine|contains:
      - SQBuAHYAbwBrAGUALQ
      - kAbgB2AG8AawBlAC0A
      - JAG4AdgBvAGsAZQAtA
      - SW52b2tlL
      - ludm9rZS
      - JbnZva2Ut
  condition: all of selection_*
falsepositives:
  - Unknown
level: high
simulation:
  - type: atomic red team
    name: Create a Process using WMI Query and an Encoded Command
    technique: T1047
    atomic_guid: 7db7a7f9-9531-4840-9b30-46220135441c
regression_tests_path: regression_data/rules/windows/process_creation/proc_creation_win_powershell_base64_invoke/info.yml
license: DRL-1.1

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

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