name: Schedule Task with Rundll32 Command Trigger
id: 75b00fd8-a0ff-11eb-8b31-acde48001122
version: 1
date: '2021-04-19'
author: Teoderick Contreras, Splunk
type: TTP
datamodel:
- Endpoint
description: The following query utilizes Windows Security EventCode 4698, `A scheduled
  task was created`, to identify suspicious tasks registered on Windows either via
  schtasks.exe OR TaskService with a command to be executed with a Rundll32. This
  technique is common in new trickbot that uses rundll32 to load is trickbot downloader.
  The search will return the first time and last time the task was registered, as
  well as the `Command` to be executed, `Task Name`, `Author`, `Enabled`, and whether
  it is `Hidden` or not. schtasks.exe is natively found in `C:\Windows\system32` and
  `C:\Windows\syswow64`. The following DLL(s) are loaded when schtasks.exe or TaskService
  is launched -`taskschd.dll`. If found loaded by another process, it is possible
  a scheduled task is being registered within that process context in memory. Upon
  triage, identify the task scheduled source. Was it schtasks.exe or via TaskService?
  Review the job created and the Command to be executed. Capture any artifacts on
  disk and review. Identify any parallel processes within the same timeframe to identify
  source.'
search: '`wineventlog_security` EventCode=4698 | xmlkv Message | search Command IN
  ("*rundll32*") | stats count min(_time) as firstTime max(_time) as lastTime by dest,
  Task_Name, Command, Author, Enabled, Hidden, Arguments | `security_content_ctime(firstTime)`
  | `security_content_ctime(lastTime)` | `schedule_task_with_rundll32_command_trigger_filter`'
how_to_implement: To successfully implement this search, you need to be ingesting
  logs with the task schedule (Exa. Security Log EventCode 4698) endpoints. Tune and
  filter known instances of Task schedule used in your environment.
known_false_positives: unknown
references:
- https://labs.vipre.com/trickbot-and-its-modules/
- https://whitehat.eu/incident-response-case-study-featuring-ryuk-and-trickbot-part-2/
tags:
  analytic_story:
  - Windows Persistence Techniques
  - Trickbot
  - IcedID
  - Living Off The Land
  confidence: 100
  context:
  - Source:Endpoint
  - Stage:Defense Evasion
  dataset:
  - https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/malware/trickbot/tasksched/windows-security.log
  impact: 70
  kill_chain_phases:
  - Exploitation
  message: A schedule task process commandline rundll32 arguments $Arguments$ in host
    $dest$
  mitre_attack_id:
  - T1053
  observable:
  - name: dest
    type: Hostname
    role:
    - Victim
  product:
  - Splunk Enterprise
  - Splunk Enterprise Security
  - Splunk Cloud
  required_fields:
  - _time
  - dest
  - Task_Name
  - Command
  - Author
  - Enabled
  - Hidden
  - Arguments
  risk_score: 70
  security_domain: endpoint
  asset_type: Endpoint