windows_powershell_scheduletask.yml

name: Windows PowerShell ScheduleTask
id: ddf82fcb-e9ee-40e3-8712-a50b5bf323fc
version: 1
date: '2023-06-12'
author: Michael Haag, Splunk
status: production
type: Anomaly
data_source:
- Powershell Script Block Logging 4104
description: "The following analytic detects potential malicious activities related to PowerShell's task scheduling cmdlets. It looks for anomalies in PowerShell logs, specifically EventCode 4104, associated with script block logging. The analytic flags unusual or suspicious use patterns of key task-related cmdlets such as 'New-ScheduledTask', 'Set-ScheduledTask', and others, which are often used by attackers for persistence and remote execution of malicious code.
  If a true positive is found, it suggests an possible attacker is attempting to persist within the environment or potentially deliver additional malicious payloads, leading to data theft, ransomware, or other damaging outcomes. To implement this analytic, PowerShell Script Block Logging needs to be enabled on some or all endpoints. Analysts should be aware of benign administrative tasks that can trigger alerts and tune the analytic accordingly to reduce false positives.
  Upon triage, review the PowerShell logs for any unusual or unexpected cmdlet usage, IP addresses, user accounts, or timestamps. If these factors align with known malicious behavior patterns, immediate mitigation steps, such as isolation of the affected systems, user account changes, and relevant threat hunting activities, should be initiated. This proactive analysis significantly enhances an organization's capacity to swiftly respond to, and potentially prevent, the execution of advanced persistent threats in their network."
search: '`powershell` EventCode=4104 ScriptBlockText IN ("*New-ScheduledTask*", "*New-ScheduledTaskAction*", "*New-ScheduledTaskSettingsSet*", "*New-ScheduledTaskTrigger*", "*Register-ClusteredScheduledTask*", "*Register-ScheduledTask*", "*Set-ClusteredScheduledTask*", "*Set-ScheduledTask*", "*Start-ScheduledTask*", "*Enable-ScheduledTask*")
  | stats count min(_time) as firstTime max(_time) as lastTime by EventCode ScriptBlockText Computer user_id
  | `security_content_ctime(firstTime)`
  | `security_content_ctime(lastTime)`
  | `windows_powershell_scheduletask_filter`'
how_to_implement: To successfully implement this analytic, you will need to enable
  PowerShell Script Block Logging on some or all endpoints. Additional setup here
  https://docs.splunk.com/Documentation/UBA/5.0.4.1/GetDataIn/AddPowerShell#Configure_module_logging_for_PowerShell.
known_false_positives: Benign administrative tasks can also trigger alerts, necessitating a firm understanding of the typical system behavior and precise tuning of the analytic to reduce false positives.
references:
- https://learn.microsoft.com/en-us/powershell/module/scheduledtasks/?view=windowsserver2022-ps
- https://thedfirreport.com/2023/06/12/a-truly-graceful-wipe-out/
tags:
  analytic_story:
  - Scheduled Tasks
  asset_type: Endpoint
  atomic_guid:
  - af9fd58f-c4ac-4bf2-a9ba-224b71ff25fd
  confidence: 50
  impact: 50
  message: The PowerShell cmdlets related to task creation, modification and start occurred on $Computer$ by $user_id$. 
  mitre_attack_id:
  - T1053.005
  - T1059.001
  - T1059
  observable:
  - name: Computer
    type: Hostname
    role:
    - Victim
  - name: user_id
    type: User
    role:
    - Victim
  product:
  - Splunk Enterprise
  - Splunk Enterprise Security
  - Splunk Cloud
  required_fields:
  - _time
  - ScriptBlockText
  - Computer
  - EventCode
  security_domain: endpoint
  risk_score: 25
tests:
- name: True Positive Test
  attack_data:
  - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1053.005/atomic_red_team/pwsh_scheduledtask.log
    source: XmlWinEventLog:Microsoft-Windows-PowerShell/Operational
    sourcetype: xmlwineventlog