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Detection rules › Sigma

Potential Persistence Via Powershell Search Order Hijacking - Task

Status
test
Severity
high
Log source
product windows, category process_creation
Author
pH-T (Nextron Systems), Florian Roth (Nextron Systems)
Source
github.com/SigmaHQ/sigma

Detects suspicious powershell execution via a schedule task where the command ends with an suspicious flags to hide the powershell instance instead of executeing scripts or commands. This could be a sign of persistence via PowerShell "Get-Variable" technique as seen being used in Colibri Loader

MITRE ATT&CK coverage

TacticTechniques
ExecutionT1053.005 Scheduled Task/Job: Scheduled Task, T1059.001 Command and Scripting Interpreter: PowerShell
PersistenceT1053.005 Scheduled Task/Job: Scheduled Task
Privilege EscalationT1053.005 Scheduled Task/Job: Scheduled Task

Event coverage

ProviderEventTitle
SysmonEvent ID 1Process creation

Rule body yaml

title: Potential Persistence Via Powershell Search Order Hijacking - Task
id: b66474aa-bd92-4333-a16c-298155b120df
related:
    - id: 6e8811ee-90ba-441e-8486-5653e68b2299
      type: similar
status: test
description: Detects suspicious powershell execution via a schedule task where the command ends with an suspicious flags to hide the powershell instance instead of executeing scripts or commands. This could be a sign of persistence via PowerShell "Get-Variable" technique as seen being used in Colibri Loader
references:
    - https://blog.malwarebytes.com/threat-intelligence/2022/04/colibri-loader-combines-task-scheduler-and-powershell-in-clever-persistence-technique/
author: pH-T (Nextron Systems), Florian Roth (Nextron Systems)
date: 2022-04-08
modified: 2023-02-03
tags:
    - attack.privilege-escalation
    - attack.execution
    - attack.persistence
    - attack.t1053.005
    - attack.t1059.001
logsource:
    product: windows
    category: process_creation
detection:
    selection:
        ParentImage: 'C:\WINDOWS\System32\svchost.exe'
        ParentCommandLine|contains|all:
            - '-k netsvcs'
            - '-s Schedule'
        CommandLine|endswith:
            - ' -windowstyle hidden'
            - ' -w hidden'
            - ' -ep bypass'
            - ' -noni'
    condition: selection
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: condition

selection

Stage 1: selection

selection:
    ParentImage: 'C:\WINDOWS\System32\svchost.exe'
    ParentCommandLine|contains|all:
        - '-k netsvcs'
        - '-s Schedule'
    CommandLine|endswith:
        - ' -windowstyle hidden'
        - ' -w hidden'
        - ' -ep bypass'
        - ' -noni'

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
CommandLineends_with
  • -ep bypass
  • -noni
  • -w hidden
  • -windowstyle hidden
ParentCommandLinematch
  • -k netsvcs
  • -s Schedule
ParentImageeq
  • C:\WINDOWS\System32\svchost.exe corpus 4 (sigma 3, elastic 1)