Detection: Gsuite Email With Known Abuse Web Service Link

Updated Date: 2025-02-10 ID: 8630aa22-042b-11ec-af39-acde48001122 Author: Teoderick Contreras, Splunk Type: Anomaly Product: Splunk Enterprise Security

Description

The following analytic detects emails in Gsuite containing links to known abuse web services such as Pastebin, Telegram, and Discord. It leverages Gsuite Gmail logs to identify emails with these specific domains in their links. This activity is significant because these services are commonly used by attackers to deliver malicious payloads. If confirmed malicious, this could lead to the delivery of malware, phishing attacks, or other harmful activities, potentially compromising sensitive information or systems within the organization.

 1`gsuite_gmail` "link_domain{}" IN ("*pastebin.com*", "*discord*", "*telegram*","t.me") 
 2| rex field=source.from_header_address "[^@]+@(?<source_domain>[^@]+)" 
 3| rex field=destination{}.address "[^@]+@(?<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 values(link_domain{}) as link_domains min(_time) as firstTime max(_time) as lastTime count by is_spam source.address source.from_header_address subject destination{}.address phase severity 
 8| `security_content_ctime(firstTime)` 
 9| `security_content_ctime(lastTime)` 
10| `gsuite_email_with_known_abuse_web_service_link_filter`

Data Source

Name Platform Sourcetype Source
G Suite Gmail N/A 'gsuite:gmail:bigquery' 'http:gsuite'

Macros Used

Name Value
gsuite_gmail sourcetype=gsuite:gmail:bigquery
gsuite_email_with_known_abuse_web_service_link_filter search *
gsuite_email_with_known_abuse_web_service_link_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
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.

Known False Positives

normal email contains this link that are known application within the organization or network can be catched by this detection.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message:

Suspicious email from $source.address$ to $destination{}.address$

Risk Object Risk Object Type Risk Score Threat Objects
destination{}.address user 25 source.address

References

Detection Testing

Test Type Status Dataset Source Sourcetype
Validation ✅ Passing N/A N/A N/A
Unit ✅ Passing Dataset http:gsuite gsuite:gmail:bigquery
Integration ✅ Passing Dataset http:gsuite gsuite:gmail:bigquery

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: 5