Detection: Windows USBSTOR Registry Key Modification

Updated Date: 2025-01-17 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` values(Registry.registry_value_data) as registry_value_data, values(Registry.registry_value_name) as registry_value_name, min(_time) as firstTime, max(_time) as lastTime, count from datamodel=Endpoint.Registry where Registry.registry_path IN ("HKLM\\System\\CurrentControlSet\\Enum\\USBSTOR\\*") AND Registry.registry_value_name ="FriendlyName" by Registry.dest,Registry.registry_value_data,Registry.registry_path
 3
 4| `drop_dm_object_name(Registry)`
 5
 6| 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)
 7
 8| `security_content_ctime(firstTime)` 
 9
10| `security_content_ctime(lastTime)` 
11
12| `windows_usbstor_registry_key_modification_filter`

Data Source

Name	Platform	Sourcetype	Source
Sysmon EventID 12	Windows	`'xmlwineventlog'`	`'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'`
Sysmon EventID 13	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_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
T1200	Hardware Additions	Initial Access
T1025	Data from Removable Media	Collection
T1091	Replication Through Removable Media	Initial Access

Delivery

Exploitation

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 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

Data Protection

Risk Based Analytics (RBA)

Risk Message:

A removable storage device named [$object_name$] with drive letter [$object_handle$] was attached to $dest$

Risk Object	Risk Object Type	Risk Score	Threat Objects
dest	system	10	object_handle, object_name

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