Rundll32 LockWorkStation

name: Rundll32 LockWorkStation
id: fa90f372-f91d-11eb-816c-acde48001122
version: 13
creation_date: '2021-08-09'
modification_date: '2026-05-13'
author: Teoderick Contreras, Splunk
status: production
type: Anomaly
description: The following analytic detects the execution of the rundll32.exe command with the user32.dll,LockWorkStation parameter, which is used to lock the workstation via command line. This detection leverages data from Endpoint Detection and Response (EDR) agents, focusing on process names and command-line executions. This activity is significant as it is an uncommon method to lock a screen and has been observed in CONTI ransomware tooling for defense evasion. If confirmed malicious, this technique could indicate an attempt to evade detection and hinder incident response efforts.
data_source:
    - Sysmon EventID 1
    - Windows Event Log Security 4688
    - CrowdStrike ProcessRollup2
search: |-
    | tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Processes
      WHERE Processes.process_name=rundll32.exe Processes.process= "*user32.dll,LockWorkStation*"
      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)`
    | `rundll32_lockworkstation_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: No false positives have been identified at this time.
references:
    - https://threadreaderapp.com/thread/1423361119926816776.html
intermediate_findings:
    entities:
        - field: dest
          type: system
          score: 20
          message: Process $process_name$ with cmdline $process$ in host $dest$
threat_objects:
    - field: process_name
      type: process_name
analytic_story:
    - Ransomware
asset_type: Endpoint
mitre_attack_id:
    - T1218.011
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: endpoint
security_domain: endpoint