Detection: Windows USBSTOR Registry Key Modification

Updated Date: 2026-05-13 ID: a345980a-417d-4ed3-9fb4-cac30c9405a0 Author: Steven Dick Type: Anomaly Product: Splunk Enterprise Security

Description

This analytic is used to identify when a USB removable media device is attached to a Windows host. In this scenario we are querying the Endpoint Registry data model to look for modifications to the HKLM\System\CurrentControlSet\Enum\USBSTOR\ key. Adversaries and Insider Threats may use removable media devices for several malicious activities, including initial access, execution, and exfiltration.

Search

 1
 2| tstats `security_content_summariesonly` min(_time) as firstTime, max(_time) as lastTime, count FROM datamodel=Endpoint.Registry
 3  WHERE Registry.registry_path IN ("HKLM\\System\\CurrentControlSet\\Enum\\USBSTOR\\*")
 4    AND
 5    Registry.registry_value_name ="FriendlyName"
 6  BY Registry.action Registry.dest Registry.process_guid
 7     Registry.process_id Registry.registry_hive Registry.registry_path
 8     Registry.registry_key_name Registry.registry_value_data Registry.registry_value_name
 9     Registry.registry_value_type Registry.status Registry.user
10     Registry.vendor_product
11
12| `drop_dm_object_name(Registry)`
13
14| eval object_name = registry_value_data, object_handle = split(mvindex(split(registry_path, "\\"),6),"&amp;"), object_handle = mvindex(mvfilter(NOT len(object_handle)=1),0)
15
16| `security_content_ctime(firstTime)`
17
18| `security_content_ctime(lastTime)`
19
20| `windows_usbstor_registry_key_modification_filter`

Data Source

Name	Platform	Sourcetype	Source
Sysmon EventID 13	Windows	`'XmlWinEventLog'`	`'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'`
Sysmon EventID 12	Windows	`'XmlWinEventLog'`	`'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'`

Macros Used

Name	Value
security_content_summariesonly	`summariesonly=`summariesonly_config `allow_old_summaries=`oldsummaries_config `fillnull_value=`fillnull_config``
windows_usbstor_registry_key_modification_filter	`search *`

windows_usbstor_registry_key_modification_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
T1025	Data from Removable Media	Collection
T1091	Replication Through Removable Media	Initial Access
T1200	Hardware Additions	Lateral Movement

Exploitation

Delivery

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 Finding (Notable)	No
Creates Intermediate Finding (Risk Event)	Yes

Anomaly detections generate Intermediate Findings (Risk Events). They do not generate a Finding (Notable) directly.

Implementation

To successfully implement this search, you must ingest endpoint logging that tracks changes to the HKLM\System\CurrentControlSet\Enum\USBSTOR\ registry keys. Ensure that the field from the event logs is being mapped to the proper fields in the Endpoint.Registry data model.

Known False Positives

Legitimate USB activity will also be detected. Please verify and investigate as appropriate.

Associated Analytic Story

Intermediate Findings

Message	Entity Field	Entity Type	Risk Score
A removable storage device named [$object_name$] with drive letter [$object_handle$] was attached to $dest$	dest	system	20

Threat Objects

Field	Type
object_name	registry_value_name
object_handle	registry_value_text

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: 8