Windows RunMRU Command Execution

name: Windows RunMRU Command Execution
id: a15aa1ab-2b79-467f-8201-65e0f32d5b1a
version: 9
date: '2026-03-10'
author: Nasreddine Bencherchali, Michael Haag, Splunk
status: production
type: Anomaly
description: The following analytic detects modifications to the Windows RunMRU registry key, which stores a history of commands executed through the Run dialog box (Windows+R). It leverages Endpoint Detection and Response (EDR) telemetry to monitor registry events targeting this key. This activity is significant as malware often uses the Run dialog to execute malicious commands while attempting to appear legitimate. If confirmed malicious, this could indicate an attacker using indirect command execution techniques for defense evasion or persistence. The detection excludes MRUList value changes to focus on actual command entries.
data_source:
    - Sysmon EventID 13
search: '| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Registry where Registry.registry_path="*\\Microsoft\\Windows\\CurrentVersion\\Explorer\\RunMRU*" NOT Registry.registry_value_name="MRUList" NOT Registry.registry_value_data="unknown" by Registry.dest Registry.registry_value_data Registry.action Registry.process_guid Registry.process_id Registry.registry_key_name Registry.user Registry.registry_path Registry.registry_hive Registry.registry_value_name Registry.status Registry.vendor_product | `drop_dm_object_name(Registry)` | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `windows_runmru_command_execution_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 `Registry` 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: This detection may generate a few false positives, such as legitimate software updates or legitimate system maintenance activities that modify the RunMRU key. However, the exclusion of MRUList value changes helps reduce the number of false positives by focusing only on actual command entries. Add any specific false positives to the built in filter to reduce findings as needed.
references:
    - https://medium.com/@ahmed.moh.farou2/fake-captcha-campaign-on-arabic-pirated-movie-sites-delivers-lumma-stealer-4f203f7adabf
    - https://medium.com/@shaherzakaria8/downloading-trojan-lumma-infostealer-through-capatcha-1f25255a0e71
    - https://www.forensafe.com/blogs/runmrukey.html
    - https://github.com/SigmaHQ/sigma/blob/master/rules-threat-hunting/windows/registry/registry_set/registry_set_runmru_command_execution.yml
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: An instance of $registry_value_data$ was identified on endpoint $dest$ by user $user$ attempting to execute a command through the Run dialog box.
    risk_objects:
        - field: dest
          type: system
          score: 20
        - field: user
          type: user
          score: 20
    threat_objects:
        - field: registry_value_data
          type: registry_value_text
tags:
    analytic_story:
        - Lumma Stealer
        - Fake CAPTCHA Campaigns
    asset_type: Endpoint
    mitre_attack_id:
        - T1202
    product:
        - Splunk Enterprise
        - Splunk Enterprise Security
        - Splunk Cloud
    security_domain: endpoint
    cve: []
    atomic_guid:
        - de323a93-2f18-4bd5-ba60-d6fca6aeff76
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1202/atomic_red_team/windows-sysmon_runmru.log
          source: XmlWinEventLog:Microsoft-Windows-Sysmon/Operational
          sourcetype: XmlWinEventLog