Detection: Detect RTLO In Process

Updated Date: 2024-09-30 ID: 22ac27b4-7189-4a4f-9375-b9017c9620d7 Author: Steven Dick Type: TTP Product: Splunk Enterprise Security

Description

The following analytic identifies the abuse of the right-to-left override (RTLO) character (U+202E) in process names. It leverages data from Endpoint Detection and Response (EDR) agents, focusing on process execution logs and command-line data. This activity is significant because adversaries use the RTLO character to disguise malicious files or commands, making them appear benign. If confirmed malicious, this technique can allow attackers to execute harmful code undetected, potentially leading to unauthorized access, data exfiltration, or further system compromise.

Search

 1
 2| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where Processes.process!=unknown AND Processes.action=allowed by Processes.dest Processes.user Processes.original_file_name Processes.parent_process_name Processes.parent_process Processes.process_name Processes.process Processes.process_id Processes.process_guid Processes.parent_process_id 
 3| `security_content_ctime(firstTime)` 
 4| `security_content_ctime(lastTime)` 
 5| `drop_dm_object_name(Processes)` 
 6| regex process="\\x{202E}" 
 7| rex field=process "(?<RTLO_command_1>.+)(?<RTLO_exist_process>\\x{202E})(?<RTLO_command_2>.+)" 
 8| eval process_with_RTLO=process 
 9| eval process=RTLO_command_1.RTLO_command_2 
10| fields - RTLO* 
11| `detect_rtlo_in_process_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_rtlo_in_process_filter	`search *`

detect_rtlo_in_process_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
T1036.002	Right-to-Left Override	Defense Evasion
T1036	Masquerading	Defense Evasion

KillChainPhase.EXPLOITAITON

NistCategory.DE_CM

Cis18Value.CIS_10

BRONZE BUTLER

BlackTech

Ferocious Kitten

Ke3chang

Scarlet Mimic

APT28

APT32

Agrius

BRONZE BUTLER

Ember Bear

FIN13

LazyScripter

Nomadic Octopus

OilRig

PLATINUM

Sandworm Team

TA551

TeamTNT

Windshift

Winter Vivern

ZIRCONIUM

menuPass

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

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

Implementation in regions that use right to left in native language.

Associated Analytic Story

Spearphishing Attachments

Risk Based Analytics (RBA)

Risk Message	Risk Score	Impact	Confidence
Suspicious RTLO detected in $process_name$ on endpoint $dest$ by user $user$.	40	50	80

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: 4