GCP Multiple Users Failing To Authenticate From Ip

Status: production
Severity: low
Group by: "event.name", "id.applicationName", _time, app, src
Author: Bhavin Patel, Splunk
Source: github.com/splunk/security_content

The following analytic detects a single source IP address failing to authenticate into more than 20 unique Google Workspace user accounts within a 5-minute window. It leverages Google Workspace login failure events to identify potential password spraying attacks. This activity is significant as it may indicate an adversary attempting to gain unauthorized access or elevate privileges within the Google Cloud Platform. If confirmed malicious, this behavior could lead to unauthorized access to sensitive resources, data breaches, or further exploitation within the environment.

Known false positives

No known false postives for this detection. Please review this alert.

MITRE ATT&CK coverage

Tactic	Techniques
Resource Development	`T1586.003` Compromise Accounts: Cloud Accounts
Credential Access	`T1110.003` Brute Force: Password Spraying `T1110.004` Brute Force: Credential Stuffing

Telemetry coverage

Platform	Record / event type
Google Workspace	login_failure: Login Failure

Rules detecting the same action

These rules filter on the same operation.

GCP Authentication Failed During MFA Challenge (Splunk)
GCP Multiple Failed MFA Requests For User (Splunk)
GCP Unusual Number of Failed Authentications From Ip (Splunk)

Rule body

name: GCP Multiple Users Failing To Authenticate From Ip
id: da20828e-d6fb-4ee5-afb7-d0ac200923d5
version: 11
creation_date: '2022-10-12'
modification_date: '2026-05-13'
author: Bhavin Patel, Splunk
status: production
type: Anomaly
description: The following analytic detects a single source IP address failing to authenticate into more than 20 unique Google Workspace user accounts within a 5-minute window. It leverages Google Workspace login failure events to identify potential password spraying attacks. This activity is significant as it may indicate an adversary attempting to gain unauthorized access or elevate privileges within the Google Cloud Platform. If confirmed malicious, this behavior could lead to unauthorized access to sensitive resources, data breaches, or further exploitation within the environment.
data_source:
    - Google Workspace
search: |-
    `gws_reports_login` event.type = login event.name = login_failure
      | bucket span=5m _time
      | stats count dc(user) AS unique_accounts values(user) as tried_accounts values(authentication_method) AS authentication_method earliest(_time) as firstTime latest(_time) as lastTime
        BY _time event.name src
           app id.applicationName
      | `security_content_ctime(firstTime)`
      | `security_content_ctime(lastTime)`
      | where unique_accounts > 20
      | `gcp_multiple_users_failing_to_authenticate_from_ip_filter`
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 `unique_accounts` threshold values according to your environment. Specifically, this analytic leverages the User log events.
known_false_positives: No known false postives for this detection. Please review this alert.
references:
    - https://cloud.google.com/blog/products/identity-security/how-google-cloud-can-help-stop-credential-stuffing-attacks
    - https://www.slideshare.net/dafthack/ok-google-how-do-i-red-team-gsuite
    - https://attack.mitre.org/techniques/T1110/003/
    - https://www.blackhillsinfosec.com/wp-content/uploads/2020/05/Breaching-the-Cloud-Perimeter-Slides.pdf
intermediate_findings:
    entities:
        - field: tried_accounts
          type: user
          score: 20
          message: 'Multiple failed login attempts (Count: $unique_accounts$) against users seen from $src$'
threat_objects:
    - field: src
      type: ip_address
analytic_story:
    - GCP Account Takeover
asset_type: Google Cloud Platform tenant
mitre_attack_id:
    - T1110.003
    - T1110.004
    - T1586.003
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: cloud
security_domain: threat

Stages and Predicates

Stage 1: `search`

`gws_reports_login` event.type = login event.name = login_failure

Stage 2: `bucket`

| bucket span=5m _time

Stage 3: `stats`

| stats count dc(user) AS unique_accounts values(user) as tried_accounts values(authentication_method) AS authentication_method earliest(_time) as firstTime latest(_time) as lastTime
    BY _time event.name src
       app id.applicationName

Stage 4: `search`

| `security_content_ctime(firstTime)`

Stage 5: `search`

| `security_content_ctime(lastTime)`

Stage 6: `where`

| where unique_accounts > 20

Stage 7: `search`

| `gcp_multiple_users_failing_to_authenticate_from_ip_filter`

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`event.name`	eq	`login_failure`	`field:"event.name" kind:eq value:"login_failure"`
`event.type`	eq	`login`	`field:"event.type" kind:eq value:"login"`
`sourcetype`	eq	`gws:reports:login`	`field:"sourcetype" kind:eq value:"gws:reports:login"`
`unique_accounts`	gt	`20`	`field:"unique_accounts" kind:gt value:"20"`

GCP Multiple Users Failing To Authenticate From Ip

Known false positives

MITRE ATT&CK coverage

Telemetry coverage

Rules detecting the same action

Rule body

Stages and Predicates

Stage 1: search

Stage 2: bucket

Stage 3: stats

Stage 4: search

Stage 5: search

Stage 6: where

Stage 7: search