Windows ComputerDefaults Spawning a Process

name: Windows ComputerDefaults Spawning a Process
id: 697eb4c0-1008-4c3c-b5ae-7bd9b39adbd6
version: 4
date: '2026-03-10'
author: Teoderick Contreras, Splunk
status: production
type: TTP
description: The following analytic detects the spawning of ComputerDefaults.exe, a Windows system process used to manage default application associations. While normally legitimate, this process can be exploited by attackers to bypass User Account Control (UAC) and execute unauthorized code with elevated privileges. Detection focuses on abnormal execution patterns, unusual parent-child process relationships, or deviations from standard paths. Such behavior may indicate attempts to modify system defaults or run malicious scripts undetected. Monitoring ComputerDefaults.exe is critical to identify potential security threats, prevent privilege escalation, and maintain system integrity by distinguishing normal operations from suspicious activity.
data_source:
    - Sysmon EventID 1
search: |-
    | tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Processes
      WHERE Processes.parent_process_name=ComputerDefaults.exe
      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)`
    | `windows_computerdefaults_spawning_a_process_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://www.recordedfuture.com/research/from-castleloader-to-castlerat-tag-150-advances-operations
drilldown_searches:
    - name: View the detection results for - "$dest$"
      search: '%original_detection_search% | search  dest = "$dest$"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
    - name: View risk events for the last 7 days for - "$dest$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$dest$") starthoursago=168  | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
rba:
    message: A ComputerDefaults.exe process $parent_process_name$ spawning child process $process_name$ on host $dest$
    risk_objects:
        - field: dest
          type: system
          score: 50
    threat_objects:
        - field: parent_process_name
          type: parent_process_name
tags:
    analytic_story:
        - Castle RAT
        - BlankGrabber Stealer
    asset_type: Endpoint
    mitre_attack_id:
        - T1548.002
    product:
        - Splunk Enterprise
        - Splunk Enterprise Security
        - Splunk Cloud
    security_domain: endpoint
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1548.002/computerdefaults_spawn_proc/computerdefaults_process.log
          source: XmlWinEventLog:Microsoft-Windows-Sysmon/Operational
          sourcetype: XmlWinEventLog