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
|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
- CIS 3
- CIS 5
- CIS 16
1 2 3 4 5 `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`
The SPL above uses the following Macros:
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.
List of fields required to use this analytic.
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
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
|54.0||60||90||Multiple Failed MFA requests for user $user$|
The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.
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