Detection: Gsuite Drive Share In External Email

EXPERIMENTAL DETECTION

This detection status is set to experimental. The Splunk Threat Research team has not yet fully tested, simulated, or built comprehensive datasets for this detection. As such, this analytic is not officially supported. If you have any questions or concerns, please reach out to us at research@splunk.com.

Updated Date: 2024-05-21 ID: f6ee02d6-fea0-11eb-b2c2-acde48001122 Author: Teoderick Contreras, Splunk Type: Anomaly Product: Splunk Enterprise Security

Description

The following analytic detects Google Drive or Google Docs files shared externally from an internal domain. It leverages GSuite Drive logs, extracting and comparing the source and destination email domains to identify external sharing. This activity is significant as it may indicate potential data exfiltration by an attacker or insider. If confirmed malicious, this could lead to unauthorized access to sensitive information, data leakage, and potential compliance violations. Monitoring this behavior helps in early detection and mitigation of data breaches.

Search

 1`gsuite_drive` NOT (email IN("", "null")) 
 2| rex field=parameters.owner "[^@]+@(?<src_domain>[^@]+)" 
 3| rex field=email "[^@]+@(?<dest_domain>[^@]+)" 
 4| where src_domain = "internal_test_email.com" and not dest_domain = "internal_test_email.com" 
 5| eval phase="plan" 
 6| eval severity="low" 
 7| stats values(parameters.doc_title) as doc_title, values(parameters.doc_type) as doc_types, values(email) as dst_email_list, values(parameters.visibility) as visibility, values(parameters.doc_id) as doc_id, count min(_time) as firstTime max(_time) as lastTime by parameters.owner ip_address phase severity  
 8| rename parameters.owner as user ip_address as src_ip 
 9| `security_content_ctime(firstTime)` 
10| `security_content_ctime(lastTime)` 
11| `gsuite_drive_share_in_external_email_filter`

Data Source

Name	Platform	Sourcetype	Source	Supported App
G Suite Drive	N/A	`'gsuite:drive:json'`	`'http:gsuite'`	N/A

Macros Used

Name	Value
gsuite_drive	`sourcetype=gsuite:drive:json`
gsuite_drive_share_in_external_email_filter	`search *`

gsuite_drive_share_in_external_email_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
T1567.002	Exfiltration to Cloud Storage	Exfiltration
T1567	Exfiltration Over Web Service	Exfiltration

KillChainPhase.ACTIONS_ON_OBJECTIVES

NistCategory.DE_AE

Cis18Value.CIS_10

Akira

Chimera

Cinnamon Tempest

Confucius

Earth Lusca

FIN7

HAFNIUM

HEXANE

Kimsuky

Leviathan

LuminousMoth

POLONIUM

Scattered Spider

Threat Group-3390

ToddyCat

Turla

Wizard Spider

ZIRCONIUM

APT28

Magic Hound

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 need to be ingesting logs related to gsuite having the file attachment metadata like file type, file extension, source email, destination email, num of attachment and etc. In order for the search to work for your environment, please edit the query to use your company specific email domain instead of internal_test_email.com.

Known False Positives

network admin or normal user may share files to customer and external team.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message	Risk Score	Impact	Confidence
suspicious share gdrive from $parameters.owner$ to $email$ namely as $parameters.doc_title$	72	80	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

https://www.redhat.com/en/topics/devops/what-is-devsecops

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	Not Applicable	N/A	N/A	N/A
Unit	✅ Passing	Dataset	`http:gsuite`	`gsuite:drive:json`
Integration	✅ Passing	Dataset	`http:gsuite`	`gsuite:drive:json`

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: 2