Detection: Detect Renamed RClone

Updated Date: 2024-10-17 ID: 6dca1124-b3ec-11eb-9328-acde48001122 Author: Michael Haag, Splunk Type: Hunting Product: Splunk Enterprise Security

Description

The following analytic detects the execution of a renamed rclone.exe process, which is commonly used for data exfiltration to remote destinations. This detection leverages Endpoint Detection and Response (EDR) telemetry, focusing on process names and original file names that do not match. This activity is significant because ransomware groups often use RClone to exfiltrate sensitive data. If confirmed malicious, this behavior could indicate an ongoing data exfiltration attempt, potentially leading to significant data loss and further compromise of the affected systems.

Search

1
2| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where (Processes.original_file_name=rclone.exe AND Processes.process_name!=rclone.exe) by Processes.dest Processes.user Processes.parent_process_name Processes.process_name Processes.process Processes.process_id Processes.parent_process_id Processes.original_file_name 
3| `drop_dm_object_name(Processes)` 
4| `security_content_ctime(firstTime)` 
5| `security_content_ctime(lastTime)` 
6| `detect_renamed_rclone_filter`

Data Source

Name	Platform	Sourcetype	Source
CrowdStrike ProcessRollup2	N/A	`'crowdstrike:events:sensor'`	`'crowdstrike'`
Sysmon EventID 1	Windows	`'xmlwineventlog'`	`'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'`
Windows Event Log Security 4688	Windows	`'xmlwineventlog'`	`'XmlWinEventLog:Security'`

Macros Used

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

detect_renamed_rclone_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
T1020	Automated Exfiltration	Exfiltration

KillChainPhase.ACTIONS_ON_OBJECTIVES

NistCategory.DE_AE

Cis18Value.CIS_10

Gamaredon Group

Ke3chang

RedCurl

Sidewinder

Tropic Trooper

Winter Vivern

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	False

This configuration file applies to all detections of type hunting.

Implementation

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 Processes 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

False positives should be limited as this analytic identifies renamed instances of rclone.exe. Filter as needed if there is a legitimate business use case.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message	Risk Score	Impact	Confidence
The following $process_name$ has been identified as renamed, spawning from $parent_process_name$ on $dest$ by $user$.	27	30	90

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: 5