Detection: Windows RunMRU Registry Key or Value Deleted

Updated Date: 2025-11-20 ID: e651795f-b2c9-4a84-a18a-b901018a3bfa Author: Teoderick Contreras, Splunk Type: Anomaly Product: Splunk Enterprise Security

Description

The following analytic detects the deletion or modification of Most Recently Used (MRU) command entries stored within the Windows Registry. Adversaries often clear these registry keys, such as HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\RunMRU, to remove forensic evidence of commands executed via the Windows Run dialog or other system utilities. This activity aims to obscure their actions, hinder incident response efforts, and evade detection. Detection focuses on monitoring for changes (deletion of values or modification of the MRUList value) to these specific registry paths, particularly when performed by unusual processes or outside of typical user behavior. Anomalous deletion events can indicate an attempt at defense evasion or post-exploitation cleanup by a malicious actor.

Search

1
2| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Registry where Registry.registry_path = "*\\Software\\Microsoft\\Windows\\CurrentVersion\\Explorer\\RunMRU*" Registry.action = deleted by Registry.action Registry.dest Registry.process_guid Registry.process_id Registry.registry_hive Registry.registry_path Registry.registry_key_name Registry.registry_value_data Registry.registry_value_name Registry.registry_value_type Registry.status Registry.user Registry.vendor_product 
3| `drop_dm_object_name(Registry)` 
4| `security_content_ctime(firstTime)` 
5| `security_content_ctime(lastTime)` 
6| `windows_runmru_registry_key_or_value_deleted_filter`

Data Source

Name	Platform	Sourcetype	Source
Sysmon EventID 12	Windows	`'XmlWinEventLog'`	`'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'`

Macros Used

Name	Value
security_content_ctime	`convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$)`
windows_runmru_registry_key_or_value_deleted_filter	`search *`

windows_runmru_registry_key_or_value_deleted_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK

+ Kill Chain Phases

+ NIST

+ CIS

- Threat Actors

ID	Technique	Tactic
T1112	Modify Registry	Defense Evasion

Exploitation

Installation

DE.AE

CIS 10

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Setting	Value
Disabled	true
Cron Schedule	`0 * * * *`
Earliest Time	`-70m@m`
Latest Time	`-10m@m`
Schedule Window	`auto`
Creates Risk Event	True

This configuration file applies to all detections of type anomaly. These detections will use Risk Based Alerting.

Implementation

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. In addition, confirm the latest CIM App 4.20 or higher is installed and the latest TA for the endpoint product.

Known False Positives

This event can be seen when administrator delete a history manually or uninstall/reinstall a software that creates MRU registry entry. It is recommended to check this alert with high priority.

Associated Analytic Story

NetSupport RMM Tool Abuse

Risk Based Analytics (RBA)

Risk Message:

A most recent used entry was deleted on $dest$ within the Windows registry.

Risk Object	Risk Object Type	Risk Score	Threat Objects
dest	system	10	No Threat Objects

References

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	✅ Passing	N/A	N/A	N/A
Unit	✅ Passing	Dataset	`XmlWinEventLog:Microsoft-Windows-Sysmon/Operational`	`XmlWinEventLog`
Integration	✅ Passing	Dataset	`XmlWinEventLog:Microsoft-Windows-Sysmon/Operational`	`XmlWinEventLog`

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: GitHub | Version: 1