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Detection rules › Sigma

Add Windows Capability Via PowerShell Script

Status
test
Severity
medium
Log source
category ps_script, product windows
Author
Nasreddine Bencherchali (Nextron Systems)
Source
github.com/SigmaHQ/sigma

Detects usage of the "Add-WindowsCapability" cmdlet to add Windows capabilities. Notable capabilities could be "OpenSSH" and others.

Known false positives

  • Legitimate usage of the capabilities by administrators or users. Add additional filters accordingly.

MITRE ATT&CK coverage

TacticTechniques
ExecutionNo specific technique

Telemetry coverage

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

Rule body

title: Add Windows Capability Via PowerShell Script
id: 155c7fd5-47b4-49b2-bbeb-eb4fab335429
related:
    - id: b36d01a3-ddaf-4804-be18-18a6247adfcd
      type: similar
status: test
description: Detects usage of the "Add-WindowsCapability" cmdlet to add Windows capabilities. Notable capabilities could be "OpenSSH" and others.
references:
    - https://learn.microsoft.com/en-us/windows-server/administration/openssh/openssh_install_firstuse?tabs=powershell
    - https://www.virustotal.com/gui/file/af1c82237b6e5a3a7cdbad82cc498d298c67845d92971bada450023d1335e267/content
author: Nasreddine Bencherchali (Nextron Systems)
date: 2023-01-22
modified: 2023-05-09
tags:
    - attack.execution
logsource:
    product: windows
    category: ps_script
    definition: 'Requirements: Script Block Logging must be enabled'
detection:
    selection_cmdlet:
        ScriptBlockText|contains: 'Add-WindowsCapability '
    selection_capa:
        ScriptBlockText|contains: '-Name OpenSSH.' # For both "OpenSSH.Server" and "OpenSSH.Client"
    condition: all of selection_*
falsepositives:
    - Legitimate usage of the capabilities by administrators or users. Add additional filters accordingly.
level: medium

Stages and Predicates

Stage 0: condition

all of selection_*

Stage 1: selection_cmdlet

selection_cmdlet:
    ScriptBlockText|contains: 'Add-WindowsCapability '

Stage 2: selection_capa

selection_capa:
    ScriptBlockText|contains: '-Name OpenSSH.'

Indicators

These rows show field, operator, and value matches.

FieldKindValuesSearch
ScriptBlockTextmatch
  • -Name OpenSSH.
  • Add-WindowsCapability
field:"ScriptBlockText" kind:match