splApache-2.0from splunk/security_content

Rundll32 LockWorkStation

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.

Quality

FP risk

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Rule sourcedetections/endpoint/rundll32_lockworkstation.yml

| 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`