Detection: Remcos RAT File Creation in Remcos Folder

Updated Date: 2024-09-30 ID: 25ae862a-1ac3-11ec-94a1-acde48001122 Author: Teoderick Contreras, Splunk, Sanjay Govind Type: TTP Product: Splunk Enterprise Security

Description

The following analytic detects the creation of files in the Remcos folder within the AppData directory, specifically targeting keylog and clipboard log files. It leverages the Endpoint.Filesystem data model to identify .dat files created in paths containing "remcos." This activity is significant as it indicates the presence of the Remcos RAT, which performs keylogging, clipboard capturing, and audio recording. If confirmed malicious, this could lead to unauthorized data exfiltration and extensive surveillance capabilities for the attacker.

Search

1
2|tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Filesystem where Filesystem.file_name IN ("*.dat") Filesystem.file_path = "*\\remcos\\*" by _time Filesystem.file_name Filesystem.file_path Filesystem.dest Filesystem.file_create_time 
3| `drop_dm_object_name(Filesystem)` 
4| `security_content_ctime(firstTime)` 
5| `security_content_ctime(lastTime)` 
6| `remcos_rat_file_creation_in_remcos_folder_filter`

Data Source

Name	Platform	Sourcetype	Source
Sysmon EventID 11	Windows	`'xmlwineventlog'`	`'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'`

Macros Used

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

remcos_rat_file_creation_in_remcos_folder_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
T1113	Screen Capture	Collection

KillChainPhase.EXPLOITAITON

NistCategory.DE_CM

Cis18Value.CIS_10

APT28

APT39

BRONZE BUTLER

Dark Caracal

Dragonfly

FIN7

GOLD SOUTHFIELD

Gamaredon Group

Group5

Magic Hound

MoustachedBouncer

MuddyWater

OilRig

Silence

Volt Typhoon

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 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 process name, parent process, and command-line executions from your endpoints. If you are using Sysmon, you must have at least version 6.0.4 of the Sysmon TA.

Known False Positives

unknown

Associated Analytic Story

Remcos

Risk Based Analytics (RBA)

Risk Message	Risk Score	Impact	Confidence
file $file_name$ created in $file_path$ of $dest$	100	100	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: 4