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 |
T1078.004 | Cloud Accounts | Initial Access |
Detection: GCP Multiple Failed MFA Requests For User
Description
The following analytic detects multiple failed multi-factor authentication (MFA) requests for a single user within a Google Cloud Platform (GCP) tenant. It triggers when 10 or more MFA prompts fail within a 5-minute window, using Google Workspace login failure events. This behavior is significant as it may indicate an adversary attempting to bypass MFA by bombarding the user with repeated authentication requests. If confirmed malicious, this activity could lead to unauthorized access, allowing attackers to compromise accounts and potentially escalate privileges within the GCP environment.
Search
1`gws_reports_login` event.name=login_failure `gws_login_mfa_methods`
2| bucket span=5m _time
3| stats dc(_raw) AS mfa_prompts values(user) AS user by src_ip, login_challenge_method, _time
4| where mfa_prompts >= 10
5| `gcp_multiple_failed_mfa_requests_for_user_filter`
Data Source
Name | Platform | Sourcetype | Source |
---|---|---|---|
Google Workspace login_failure | 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_multiple_failed_mfa_requests_for_user_filter | search * |
gcp_multiple_failed_mfa_requests_for_user_filter
is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
Annotations
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 |
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. 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
Risk Based Analytics (RBA)
Risk Message | Risk Score | Impact | Confidence |
---|---|---|---|
Multiple Failed MFA requests for user $user$ | 54 | 60 | 90 |
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: 2