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This search is to detect a suspicious rundll32 commandline to update a user's system parameters related to desktop backgrounds, display settings, and visual themes. Specifically, it triggers the system to refresh and apply changes to the user-specific settings, such as wallpaper modifications or visual theme updates, ensuring that the changes take effect without the need to restart the system or log out and log back in. This technique was seen in Rhysida Ransomware and script as part of its defense evasion. This technique is not a common practice to lock a screen and maybe a good indicator of compromise. This command could also potentially be exploited by malware to disguise its activities or make unauthorized changes to a user's system settings without their knowledge or consent.

  • Type: TTP
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Endpoint
  • Last Updated: 2023-12-12
  • Author: Teoderick Contreras, Splunk
  • ID: b9fb8d97-dbc9-4a09-804c-ff0e3862bb2d




ID Technique Tactic
T1218 System Binary Proxy Execution Defense Evasion
T1218.011 Rundll32 Defense Evasion
Kill Chain Phase
  • Exploitation
  • DE.CM
  • CIS 10
| 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,UpdatePerUserSystemParameters*" by Processes.dest Processes.user Processes.parent_process Processes.process_name Processes.process Processes.process_id Processes.parent_process_id Processes.parent_process_name 
| `drop_dm_object_name(Processes)` 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `windows_rundll32_apply_user_settings_changes_filter`


The SPL above uses the following Macros:

:information_source: windows_rundll32_apply_user_settings_changes_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required fields

List of fields required to use this analytic.

  • _time
  • Processes.dest
  • Processes.user
  • Processes.parent_process
  • Processes.parent_process_name
  • Processes.process_name
  • Processes.process
  • Processes.process_id
  • Processes.parent_process_id

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


Associated Analytic Story


Risk Score Impact Confidence Message
25.0 50 50 Process $process_name$ with cmdline $process$ in host $dest$

:information_source: The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.


Test Dataset

Replay any dataset to Splunk Enterprise by using our tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

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