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Description

The following analytic identifies multiple failed multi-factor authentication requests for a single user within a Google Cloud Platform tenant. Specifically, the analytic triggers when 10 or more MFA user prompts fail within 5 minutes. Google CLoud tenants can be very different depending on the organization, Security teams should test this detection and customize these arbitrary thresholds. The detected behavior may represent an adversary who has obtained legitimate credentials for a user and continuously repeats login attempts in order to bombard users with MFA push notifications, SMS messages, and phone calls potentially resulting in the user finally accepting the authentication request. Threat actors like the Lapsus team and APT29 have leveraged this technique to bypass multi-factor authentication controls as reported by Mandiant and others.

  • Type: TTP

  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud

  • Last Updated: 2022-10-14
  • Author: Mauricio Velazco, Splunk
  • ID: cbb3cb84-c06f-4393-adcc-5cb6195621f1

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1586 Compromise Accounts Resource Development
T1586.003 Cloud Accounts Resource Development
T1621 Multi-Factor Authentication Request Generation Credential Access
T1078 Valid Accounts Defense Evasion, Persistence, Privilege Escalation, Initial Access
T1078.004 Cloud Accounts Defense Evasion, Persistence, Privilege Escalation, Initial Access
Kill Chain Phase
  • Exploitation
NIST
  • DE.CM
CIS20
  • CIS 3
  • CIS 5
  • CIS 16
CVE 


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 `gws_reports_login` event.name=login_failure `gws_login_mfa_methods` 
| bucket span=5m _time 
| stats dc(_raw) AS mfa_prompts values(user) by src_ip, login_challenge_method,  _time 
| where mfa_prompts >= 10 
| `gcp_multiple_failed_mfa_requests_for_user_filter`

Macros

The SPL above uses the following Macros:

:information_source: gcp_multiple_failed_mfa_requests_for_user_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

How To Implement

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. We would also recommend tuning the detection by adjusting the window span and mfa_prompts threshold values according to your environment. Specifically, this analytic leverages the User log events.

Known False Positives

Multiple Failed MFA requests may also be a sign of authentication or application issues. Filter as needed.

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
54.0 60 90 Multiple Failed MFA requests for user $user$

:information_source: 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

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

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