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Description

The following analytic detects modifications to the Windows registry aimed at preventing wallpaper changes. It leverages data from the Endpoint.Registry datamodel, specifically monitoring changes to the "NoChangingWallPaper" registry value. This activity is significant as it is a known tactic used by Rhysida ransomware to enforce a malicious wallpaper, thereby limiting user control over system settings. If confirmed malicious, this registry change could indicate a ransomware infection, leading to further system compromise and user disruption.

  • Type: TTP
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Endpoint
  • Last Updated: 2024-05-30
  • Author: Teoderick Contreras, Splunk
  • ID: a2276412-e254-4e9a-9082-4d92edb6a3e0

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1112 Modify Registry Defense Evasion
Kill Chain Phase
  • Exploitation
NIST
  • DE.CM
CIS20
  • CIS 10
CVE 


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| tstats `security_content_summariesonly` count FROM datamodel=Endpoint.Registry WHERE (Registry.registry_path= "*\\Windows\\CurrentVersion\\Policies\\ActiveDesktop\\NoChangingWallPaper" Registry.registry_value_data = 1) BY _time span=1h Registry.dest Registry.user Registry.registry_path Registry.registry_key_name Registry.registry_value_name Registry.registry_value_data Registry.process_guid 
| `drop_dm_object_name(Registry)` 
| where isnotnull(registry_value_data) 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `windows_modify_registry_nochangingwallpaper_filter`

Macros

The SPL above uses the following Macros:

:information_source: windows_modify_registry_nochangingwallpaper_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
  • Registry.registry_key_name
  • Registry.registry_path
  • Registry.user
  • Registry.dest
  • Registry.registry_value_name
  • Registry.action

How To Implement

To successfully implement this search you need to be ingesting information on process that include the name of the process responsible for the changes from your endpoints into the Endpoint datamodel in the Registry node. Also make sure that this registry was included in your config files ex. sysmon config to be monitored.

Known False Positives

Administrators may enable or disable this feature that may cause some false positive, however is not common. Filter as needed.

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
36.0 60 60 the registry settings was modified to disable changing of wallpaper on $dest$.

: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.

Reference

Test Dataset

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

source | version: 2