Detection: GCP Successful Single-Factor Authentication

Updated Date: 2024-11-14 ID: 40e17d88-87da-414e-b253-8dc1e4f9555b Author: Bhavin Patel, Mauricio Velazco, Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic identifies a successful single-factor authentication event against Google Cloud Platform (GCP) for an account without Multi-Factor Authentication (MFA) enabled. It uses Google Workspace login event data to detect instances where MFA is not utilized. This activity is significant as it may indicate a misconfiguration, policy violation, or potential account takeover attempt. If confirmed malicious, an attacker could gain unauthorized access to GCP resources, potentially leading to data breaches, service disruptions, or further exploitation within the cloud environment.

1`gws_reports_login` event.name=login_success NOT `gws_login_mfa_methods` 
2| stats count min(_time) as firstTime max(_time) as lastTime by user, src_ip,  login_challenge_method, app, event.name, vendor_account, action 
3|`security_content_ctime(firstTime)` 
4| `security_content_ctime(lastTime)`
5| `gcp_successful_single_factor_authentication_filter`

Data Source

Name Platform Sourcetype Source
Google Workspace login_success N/A 'gws:reports:admin' 'gws:reports:admin'

Macros Used

Name Value
gws_login_mfa_methods event.parameters{}.multiValue{} IN ("backup_code", "google_authenticator", "google_prompt", "idv_any_phone", "idv_preregistered_phone", "internal_two_factor", "knowledge_employee_id", "knowledge_preregistered_email", "login_location", "knowledge_preregistered_phone", "offline_otp", "security_key", "security_key_otp")
gcp_successful_single_factor_authentication_filter search *
gcp_successful_single_factor_authentication_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
T1586 Compromise Accounts Resource Development
T1586.003 Cloud Accounts Resource Development
T1078 Valid Accounts Defense Evasion
T1078.004 Cloud Accounts Initial Access
Delivery
Exploitation
Installation
Weaponization
DE.CM
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 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

You must install the latest version of Splunk Add-on for Google Workspace from Splunkbase (https://splunkbase.splunk.com/app/5556) which allows Splunk administrators to collect Google Workspace event data in Splunk using Google Workspace APIs. Specifically, this analytic leverages the User log events.

Known False Positives

Although not recommended, certain users may be required without multi-factor authentication. Filter as needed

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message:

Successful authentication for user $user$ without MFA

Risk Object Risk Object Type Risk Score Threat Objects
user user 45 src_ip

References

Detection Testing

Test Type Status Dataset Source Sourcetype
Validation ✅ Passing N/A N/A N/A
Unit ✅ Passing Dataset gws:reports:login gws:reports:login
Integration ✅ Passing Dataset gws:reports:login gws:reports:login

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