Detection: Windows Modify Registry ValleyRat PWN Reg Entry

Updated Date: 2024-09-30 ID: 6947c44e-be1f-4dd9-b198-bc42be5be196 Author: Teoderick Contreras, Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic detects modifications to the Windows Registry specifically targeting .pwn file associations related to the ValleyRAT malware. ValleyRAT may create or alter registry entries to associate .pwn files with malicious processes, allowing it to execute harmful scripts or commands when these files are opened. By monitoring for unusual changes in registry keys linked to .pwn extensions, this detection enables security analysts to identify potential ValleyRAT infection attempts. Early detection of these modifications helps mitigate unauthorized execution and prevents further exploitation of the system.

Search

1
2| tstats `security_content_summariesonly` count FROM datamodel=Endpoint.Registry WHERE (Registry.registry_path= "*.pwn\\Shell\\Open\\command" OR Registry.registry_value_data = ".pwn") BY Registry.dest Registry.user Registry.registry_path Registry.registry_key_name Registry.registry_value_name Registry.registry_value_data Registry.process_guid 
3| `drop_dm_object_name(Registry)` 
4| `security_content_ctime(firstTime)` 
5| `security_content_ctime(lastTime)` 
6| `windows_modify_registry_valleyrat_pwn_reg_entry_filter`

Data Source

Name	Platform	Sourcetype	Source
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_modify_registry_valleyrat_pwn_reg_entry_filter	`search *`

windows_modify_registry_valleyrat_pwn_reg_entry_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

KillChainPhase.EXPLOITAITON

NistCategory.DE_CM

Cis18Value.CIS_10

APT19

APT32

APT38

APT41

Aquatic Panda

Blue Mockingbird

Dragonfly

Earth Lusca

Ember Bear

FIN8

Gamaredon Group

Gorgon Group

Indrik Spider

Kimsuky

LuminousMoth

Magic Hound

Patchwork

Saint Bear

Silence

TA505

Threat Group-3390

Turla

Volt Typhoon

Wizard Spider

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 Notable	Yes
Rule Title	`%name%`
Rule Description	`%description%`
Notable Event Fields	user, dest
Creates Risk Event	True

This configuration file applies to all detections of type TTP. These detections will use Risk Based Alerting and generate Notable Events.

Implementation

To successfully implement this search, you need to be ingesting logs with the registry value name, registry path, and registry value data from your endpoints. If you are using Sysmon, you must have at least version 2.0 of the offical Sysmon TA. https://splunkbase.splunk.com/app/5709

Known False Positives

unknown

Associated Analytic Story

ValleyRAT

Risk Based Analytics (RBA)

Risk Message	Risk Score	Impact	Confidence
A possible ValleyRAT Registry modification in [$dest$].	90	90	100

The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

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: 3