Windows Scheduled Task Service Spawned Shell

SPLUNK detection rule by Steven Dick · Apache-2.0

The following analytic detects when the Task Scheduler service ("svchost.exe -k netsvcs -p -s Schedule") spawns common command line, scripting, or shell execution binaries such as "powershell.exe" or "cmd.exe". This detection leverages data from Endpoint Detection and Response (EDR) agents, focusing on process and parent process relationships. This activity is significant as attackers often abuse the Task Scheduler for execution and persistence, blending in with legitimate Windows operations. If confirmed malicious, this could allow attackers to execute arbitrary code, maintain persistence, or escalate privileges within the environment.

name: Windows Scheduled Task Service Spawned Shell
id: d8120352-3b62-4e3c-8cb6-7b47584dd5e8
version: 12
creation_date: '2023-07-11'
modification_date: '2026-05-13'
author: Steven Dick
status: production
type: TTP
description: |
    The following analytic detects when the Task Scheduler service ("svchost.exe -k netsvcs -p -s Schedule") spawns common command line, scripting, or shell execution binaries such as "powershell.exe" or "cmd.exe".
    This detection leverages data from Endpoint Detection and Response (EDR) agents, focusing on process and parent process relationships.
    This activity is significant as attackers often abuse the Task Scheduler for execution and persistence, blending in with legitimate Windows operations.
    If confirmed malicious, this could allow attackers to execute arbitrary code, maintain persistence, or escalate privileges within the environment.
data_source:
    - Sysmon EventID 1
    - CrowdStrike ProcessRollup2
search: |-
    | tstats `security_content_summariesonly`
    count min(_time) as firstTime
          max(_time) as lastTime

    from datamodel=Endpoint.Processes where

    Processes.parent_process_name="svchost.exe"
    Processes.parent_process="*-k*"
    Processes.parent_process= "*netsvcs*"
    Processes.parent_process="*-p*"
    Processes.parent_process="*-s*"
    Processes.parent_process="*Schedule*"
    Processes.process_name IN(
        "bash.exe",
        "cmd.exe",
        "cscript.exe",
        "ksh.exe",
        "powershell.exe",
        "pwsh.exe",
        "scrcons.exe",
        "sh.exe",
        "wscript.exe",
        "zsh.exe"
    )

    by Processes.action Processes.dest Processes.original_file_name
       Processes.parent_process Processes.parent_process_exec
       Processes.parent_process_guid Processes.parent_process_id
       Processes.parent_process_name Processes.parent_process_path
       Processes.process Processes.process_exec Processes.process_guid
       Processes.process_hash Processes.process_id Processes.process_integrity_level
       Processes.process_name Processes.process_path Processes.user
       Processes.user_id Processes.vendor_product

    | `drop_dm_object_name(Processes)`
    | `security_content_ctime(firstTime)`
    | `security_content_ctime(lastTime)`
    | `windows_scheduled_task_service_spawned_shell_filter`
how_to_implement: |
    The detection is based on data that originates from Endpoint Detection and Response (EDR) agents. These agents are designed to provide security-related telemetry from the endpoints where the agent is installed. To implement this search, you must ingest logs that contain the process GUID, process name, and parent process. Additionally, you must ingest complete command-line executions. These logs must be processed using the appropriate Splunk Technology Add-ons that are specific to the EDR product. The logs must also be mapped to the `Processes` node of the `Endpoint` data model. Use the Splunk Common Information Model (CIM) to normalize the field names and speed up the data modeling process.
known_false_positives: |
    Certain scheduled tasks will intentionally call a script via PowerShell or Cmd for example.
    These will trigger this detection. Evaluate if they are legitimate and apply filters as needed.
references:
    - https://www.mandiant.com/resources/blog/tracking-evolution-gootloader-operations
    - https://nasbench.medium.com/a-deep-dive-into-windows-scheduled-tasks-and-the-processes-running-them-218d1eed4cce
    - https://attack.mitre.org/techniques/T1053/005/
drilldown_searches:
    - name: View the detection results for - "$dest$" and "$user$"
      search: '%original_detection_search% | search  dest = "$dest$" user = "$user$"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
    - name: View risk events for the last 7 days for - "$dest$" and "$user$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$dest$", "$user$") | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`'
      earliest_offset: 7d
      latest_offset: "0"
finding:
    title: A windows scheduled task spawned the shell application $process_name$ on $dest$.
    entity:
        field: user
        type: user
        score: 50
intermediate_findings:
    entities:
        - field: dest
          type: system
          score: 50
          message: A windows scheduled task spawned the shell application $process_name$ on $dest$.
threat_objects:
    - field: parent_process_name
      type: parent_process_name
    - field: process
      type: process
    - field: process_name
      type: process_name
analytic_story:
    - Windows Persistence Techniques
asset_type: Endpoint
mitre_attack_id:
    - T1053.005
    - T1059
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: endpoint
security_domain: endpoint
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/malware/gootloader/partial_ttps/windows-sysmon.log
          source: XmlWinEventLog:Microsoft-Windows-Sysmon/Operational
          sourcetype: XmlWinEventLog
      test_type: unit

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