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Detection rules › Sigma

Suspicious Service DACL Modification Via Set-Service Cmdlet - PS

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

Detects usage of the "Set-Service" powershell cmdlet to configure a new SecurityDescriptor that allows a service to be hidden from other utilities such as "sc.exe", "Get-Service"...etc. (Works only in powershell 7)

MITRE ATT&CK coverage

TacticTechniques
ExecutionT1574.011 Hijack Execution Flow: Services Registry Permissions Weakness
StealthT1574.011 Hijack Execution Flow: Services Registry Permissions Weakness

Event coverage

ProviderEventTitle
PowerShellEvent ID 4104Creating Scriptblock text (MessageNumber of MessageTotal).

Rule body yaml

title: Suspicious Service DACL Modification Via Set-Service Cmdlet - PS
id: 22d80745-6f2c-46da-826b-77adaededd74
related:
    - id: a95b9b42-1308-4735-a1af-abb1c5e6f5ac
      type: similar
status: test
description: Detects usage of the "Set-Service" powershell cmdlet to configure a new SecurityDescriptor that allows a service to be hidden from other utilities such as "sc.exe", "Get-Service"...etc. (Works only in powershell 7)
references:
    - https://twitter.com/Alh4zr3d/status/1580925761996828672
    - https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.management/set-service?view=powershell-7.2
author: Nasreddine Bencherchali (Nextron Systems)
date: 2022-10-24
tags:
    - attack.persistence
    - attack.privilege-escalation
    - attack.execution
    - attack.stealth
    - attack.t1574.011
logsource:
    product: windows
    category: ps_script
    definition: 'Requirements: Script Block Logging must be enabled'
detection:
    selection_sddl_flag:
        ScriptBlockText|contains:
            - '-SecurityDescriptorSddl '
            - '-sd '
    selection_set_service:
        ScriptBlockText|contains|all:
            - 'Set-Service '
            - 'D;;'
        ScriptBlockText|contains:
            - ';;;IU'
            - ';;;SU'
            - ';;;BA'
            - ';;;SY'
            - ';;;WD'
    condition: all of selection_*
falsepositives:
    - Rare intended use of hidden services
    - Rare FP could occur due to the non linearity of the ScriptBlockText log
level: high

Stages and Predicates

Stage 0: condition

all of selection_*

Stage 1: selection_sddl_flag

selection_sddl_flag:
    ScriptBlockText|contains:
        - '-SecurityDescriptorSddl '
        - '-sd '

Stage 2: selection_set_service

selection_set_service:
    ScriptBlockText|contains|all:
        - 'Set-Service '
        - 'D;;'
    ScriptBlockText|contains:
        - ';;;IU'
        - ';;;SU'
        - ';;;BA'
        - ';;;SY'
        - ';;;WD'

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

FieldKindValues
ScriptBlockTextmatch
  • -SecurityDescriptorSddl corpus 2 (sigma 2)
  • -sd corpus 2 (sigma 2)
  • ;;;BA
  • ;;;IU
  • ;;;SU
  • ;;;SY
  • ;;;WD
  • D;;
  • Set-Service corpus 2 (sigma 2)