Gdrive suspicious file sharing

THIS IS A EXPERIMENTAL DETECTION

This detection has been marked experimental by the Splunk Threat Research team. This means we have not been able to test, simulate, or build datasets for this detection. Use at your own risk. This analytic is NOT supported.

Try in Splunk Security Cloud

Description

This search can help the detection of compromised accounts or internal users sharing potentially malicious/classified documents with users outside your organization via GSuite file sharing .

Type: Hunting
Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
Last Updated: 2021-10-24
Author: Rod Soto, Teoderick Contreras
ID: a7131dae-34e3-11ec-a2de-acde48001122

Annotations

ATT&CK

ID	Technique	Tactic
T1566	Phishing	Initial Access

Kill Chain Phase

Delivery

NIST

DE.AE

CIS20

CIS 10

CVE

Search

`gsuite_drive` name=change_user_access 
| rename parameters.* as * 
| search email = "*@yourdomain.com" target_user != "*@yourdomain.com" 
| stats count values(owner) as owner values(target_user) as target values(doc_type) as doc_type values(doc_title) as doc_title dc(target_user) as distinct_target by src_ip email 
| where distinct_target > 50 
| `gdrive_suspicious_file_sharing_filter`

Macros

The SPL above uses the following Macros:

gsuite_drive

gdrive_suspicious_file_sharing_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required fields

List of fields required to use this analytic.

_time
src_ip
parameters.owner
parameters.target_user
parameters.doc_title
parameters.doc_type

How To Implement

Need to implement Gsuite logging targeting Google suite drive activity. In order for the search to work for your environment please update yourdomain.com value in the query with the domain relavant for your organization.

Known False Positives

This is an anomaly search, you must specify your domain in the parameters so it either filters outside domains or focus on internal domains. This search may also help investigate compromise of accounts. By looking at for example source ip addresses, document titles and abnormal number of shares and shared target users.

Associated Analytic Story

RBA

Risk Score	Impact	Confidence	Message
25.0	50	50	tbd

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

Reference

https://www.splunk.com/en_us/blog/security/investigating-gsuite-phishing-attacks-with-splunk.html

Test Dataset

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 | version: 1

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