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Detection rules › Sigma

Suspicious PowerShell Invocations - Specific

Status
test
Severity
high
Log source
category ps_script, product windows
Author
Florian Roth (Nextron Systems), Jonhnathan Ribeiro
Source
github.com/SigmaHQ/sigma

Detects suspicious PowerShell invocation command parameters

MITRE ATT&CK coverage

TacticTechniques
Execution

Telemetry coverage

ProviderRecord / event type
PowerShellEvent ID 4104: Creating Scriptblock text (MessageNumber of MessageTotal).

Rule body

title: Suspicious PowerShell Invocations - Specific
id: ae7fbf8e-f3cb-49fd-8db4-5f3bed522c71
related:
    - id: fce5f582-cc00-41e1-941a-c6fabf0fdb8c
      type: obsolete
    - id: 8ff28fdd-e2fa-4dfa-aeda-ef3d61c62090
      type: similar
    - id: 536e2947-3729-478c-9903-745aaffe60d2
      type: similar
status: test
description: Detects suspicious PowerShell invocation command parameters
references:
    - Internal Research
    - https://github.com/HackTricks-wiki/hacktricks/blob/e4c7b21b8f36c97c35b7c622732b38a189ce18f7/src/windows-hardening/windows-local-privilege-escalation/privilege-escalation-with-autorun-binaries.md
author: Florian Roth (Nextron Systems), Jonhnathan Ribeiro
date: 2017-03-05
modified: 2025-02-17
tags:
    - attack.execution
    - attack.t1059.001
logsource:
    product: windows
    category: ps_script
    definition: 'Requirements: Script Block Logging must be enabled'
detection:
    selection_convert_b64:
        ScriptBlockText|contains|all:
            - '-nop'
            - ' -w '
            - 'hidden'
            - ' -c '
            - '[Convert]::FromBase64String'
    selection_iex_selection:
        ScriptBlockText|contains|all:
            - ' -w '
            - 'hidden'
            - '-noni'
            - '-nop'
            - ' -c '
            - 'iex'
            - 'New-Object'
    selection_enc_selection:
        ScriptBlockText|contains|all:
            - ' -w '
            - 'hidden'
            - '-ep'
            - 'bypass'
            - '-Enc'
    selection_reg_selection:
        ScriptBlockText|contains|all:
            - 'powershell'
            - 'reg'
            - 'add'
        ScriptBlockText|contains:
            - '\software\microsoft\windows\currentversion\run'
            - '\software\wow6432node\microsoft\windows\currentversion\run'
            - '\software\microsoft\windows\currentversion\policies\explorer\run'
    selection_webclient_selection:
        ScriptBlockText|contains|all:
            - 'bypass'
            - '-noprofile'
            - '-windowstyle'
            - 'hidden'
            - 'new-object'
            - 'system.net.webclient'
            - '.download'
    selection_iex_webclient:
        ScriptBlockText|contains|all:
            - 'iex'
            - 'New-Object'
            - 'Net.WebClient'
            - '.Download'
    filter_chocolatey:
        ScriptBlockText|contains:
            - "(New-Object System.Net.WebClient).DownloadString('https://community.chocolatey.org/install.ps1"
            - "(New-Object System.Net.WebClient).DownloadString('https://chocolatey.org/install.ps1')"
            - 'Write-ChocolateyWarning'
    condition: 1 of selection_* and not 1 of filter_*
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: condition

1 of selection_* and not 1 of filter_*

Stage 1: selection_convert_b64

selection_convert_b64:
    ScriptBlockText|contains|all:
        - '-nop'
        - ' -w '
        - 'hidden'
        - ' -c '
        - '[Convert]::FromBase64String'

Stage 2: selection_iex_selection

selection_iex_selection:
    ScriptBlockText|contains|all:
        - ' -w '
        - 'hidden'
        - '-noni'
        - '-nop'
        - ' -c '
        - 'iex'
        - 'New-Object'

Stage 3: selection_enc_selection

selection_enc_selection:
    ScriptBlockText|contains|all:
        - ' -w '
        - 'hidden'
        - '-ep'
        - 'bypass'
        - '-Enc'

Stage 4: selection_reg_selection

selection_reg_selection:
    ScriptBlockText|contains|all:
        - 'powershell'
        - 'reg'
        - 'add'
    ScriptBlockText|contains:
        - '\software\microsoft\windows\currentversion\run'
        - '\software\wow6432node\microsoft\windows\currentversion\run'
        - '\software\microsoft\windows\currentversion\policies\explorer\run'

Stage 5: selection_webclient_selection

selection_webclient_selection:
    ScriptBlockText|contains|all:
        - 'bypass'
        - '-noprofile'
        - '-windowstyle'
        - 'hidden'
        - 'new-object'
        - 'system.net.webclient'
        - '.download'

Stage 6: selection_iex_webclient

selection_iex_webclient:
    ScriptBlockText|contains|all:
        - 'iex'
        - 'New-Object'
        - 'Net.WebClient'
        - '.Download'

Stage 7: not filter_chocolatey

filter_chocolatey:
    ScriptBlockText|contains:
        - "(New-Object System.Net.WebClient).DownloadString('https://community.chocolatey.org/install.ps1"
        - "(New-Object System.Net.WebClient).DownloadString('https://chocolatey.org/install.ps1')"
        - 'Write-ChocolateyWarning'

Exclusions

The rule actively suppresses these predicates.

FieldKindExcluded valuesSearch
ScriptBlockTextmatch(New-Object System.Net.WebClient).DownloadString('https://chocolatey.org/install.ps1')excludes:ScriptBlockText field:"ScriptBlockText" value:"(New-Object System.Net.WebClient).DownloadString('https://chocolatey.org/install.ps1')"
ScriptBlockTextmatch(New-Object System.Net.WebClient).DownloadString('https://community.chocolatey.org/install.ps1excludes:ScriptBlockText field:"ScriptBlockText" value:"(New-Object System.Net.WebClient).DownloadString('https://community.chocolatey.org/install.ps1"
ScriptBlockTextmatchWrite-ChocolateyWarningexcludes:ScriptBlockText field:"ScriptBlockText" value:"Write-ChocolateyWarning"

Indicators

These rows show field, operator, and value matches.

FieldKindValuesSearch
ScriptBlockTextmatch
  • -c
  • -w
  • -Enc
  • -ep
  • -noni
  • -nop
  • -noprofile
  • -windowstyle
  • .Download
  • .download
  • Net.WebClient corpus 2 (sigma 1, splunk 1)
  • New-Object corpus 8 (sigma 7, splunk 1)
  • [Convert]::FromBase64String
  • \software\microsoft\windows\currentversion\policies\explorer\run
  • \software\microsoft\windows\currentversion\run
  • \software\wow6432node\microsoft\windows\currentversion\run
  • add
  • bypass corpus 2 (sigma 2)
  • hidden corpus 2 (sigma 2)
  • iex corpus 2 (sigma 2)
  • new-object corpus 8 (sigma 7, splunk 1)
  • powershell corpus 3 (sigma 3)
  • reg
  • system.net.webclient corpus 3 (sigma 2, splunk 1)
field:"ScriptBlockText" kind:match