Detection: Gsuite Suspicious Shared File Name

Updated Date: 2024-11-14 ID: 07eed200-03f5-11ec-98fb-acde48001122 Author: Teoderick Contreras, Splunk Type: Anomaly Product: Splunk Enterprise Security

Description

The following analytic detects shared files in Google Drive with suspicious filenames commonly used in spear phishing campaigns. It leverages GSuite Drive logs to identify documents with titles that include keywords like "dhl," "ups," "invoice," and "shipment." This activity is significant because such filenames are often used to lure users into opening malicious documents or clicking harmful links. If confirmed malicious, this activity could lead to unauthorized access, data theft, or further compromise of the user's system.

 1`gsuite_drive` parameters.owner_is_team_drive=false "parameters.doc_title" IN ("*dhl*", "* ups *", "*delivery*", "*parcel*", "*label*", "*invoice*", "*postal*", "*fedex*", "* usps *", "* express *", "*shipment*", "*Banking/Tax*","*shipment*", "*new order*") parameters.doc_type IN ("document","pdf", "msexcel", "msword", "spreadsheet", "presentation") 
 2| rex field=parameters.owner "[^@]+@(?<source_domain>[^@]+)" 
 3| rex field=parameters.target_user "[^@]+@(?<dest_domain>[^@]+)" 
 4| where not source_domain="internal_test_email.com" and dest_domain="internal_test_email.com" 
 5| eval phase="plan" 
 6| eval severity="low" 
 7| stats count min(_time) as firstTime max(_time) as lastTime by email parameters.owner parameters.target_user parameters.doc_title parameters.doc_type phase severity 
 8| rename parameters.target_user AS user 
 9| `security_content_ctime(firstTime)` 
10| `security_content_ctime(lastTime)` 
11| `gsuite_suspicious_shared_file_name_filter`

Data Source

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

Macros Used

Name Value
gsuite_drive sourcetype=gsuite:drive:json
gsuite_suspicious_shared_file_name_filter search *
gsuite_suspicious_shared_file_name_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
T1566.001 Spearphishing Attachment Initial Access
T1566 Phishing Initial Access
Delivery
DE.AE
CIS 10

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

normal user or normal transaction may contain the subject and file type attachment that this detection try to search

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message:

suspicious share gdrive from $parameters.owner$ to $email$ namely as $parameters.doc_title$

Risk Object Risk Object Type Risk Score Threat Objects
parameters.owner user 21 No Threat Objects
email user 21 No Threat Objects

References

Detection Testing

Test Type Status Dataset Source Sourcetype
Validation ✅ Passing 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: 4