splunk_escuAnomaly

GCP Unusual Number of Failed Authentications From Ip

The following analytic identifies a single source IP failing to authenticate into Google Workspace with multiple valid users, potentially indicating a Password Spraying attack. It uses Google Workspace login failure events and calculates the standard deviation for source IPs, applying the 3-sigma rule to detect unusual failed authentication attempts. This activity is significant as it may signal an adversary attempting to gain initial access or elevate privileges. If confirmed malicious, this could lead to unauthorized access, data breaches, or further exploitation within the environment.

MITRE ATT&CK

T1110.003 T1110.004 T1586.003

Detection Query

`gws_reports_login` event.type = login event.name = login_failure
  | bucket span=5m _time
  | stats  dc(user_name) AS unique_accounts values(user_name) as tried_accounts values(authentication_method) AS authentication_method
    BY _time, src
  | eventstats  avg(unique_accounts) as ip_avg , stdev(unique_accounts) as ip_std
    BY _time
  | eval  upperBound=(ip_avg+ip_std*3)
  | eval  isOutlier=if(unique_accounts > 10 and unique_accounts >= upperBound, 1, 0)
  | where isOutlier =1
  | `gcp_unusual_number_of_failed_authentications_from_ip_filter`

Author

Bhavin Patel, Splunk

Created

2026-03-10

Data Sources

Google Workspace

References

Tags

GCP Account Takeover

Raw Content

name: GCP Unusual Number of Failed Authentications From Ip
id: bd8097ed-958a-4873-87d9-44f2b4d85705
version: 9
date: '2026-03-10'
author: Bhavin Patel, Splunk
status: production
type: Anomaly
description: The following analytic identifies a single source IP failing to authenticate into Google Workspace with multiple valid users, potentially indicating a Password Spraying attack. It uses Google Workspace login failure events and calculates the standard deviation for source IPs, applying the 3-sigma rule to detect unusual failed authentication attempts. This activity is significant as it may signal an adversary attempting to gain initial access or elevate privileges. If confirmed malicious, this could lead to unauthorized access, 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  dc(user_name) AS unique_accounts values(user_name) as tried_accounts values(authentication_method) AS authentication_method
        BY _time, src
      | eventstats  avg(unique_accounts) as ip_avg , stdev(unique_accounts) as ip_std
        BY _time
      | eval  upperBound=(ip_avg+ip_std*3)
      | eval  isOutlier=if(unique_accounts > 10 and unique_accounts >= upperBound, 1, 0)
      | where isOutlier =1
      | `gcp_unusual_number_of_failed_authentications_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 positives 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
drilldown_searches:
    - name: View the detection results for - "$tried_accounts$"
      search: '%original_detection_search% | search  tried_accounts = "$tried_accounts$"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
    - name: View risk events for the last 7 days for - "$tried_accounts$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$tried_accounts$") starthoursago=168  | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
rba:
    message: 'Unusual number of failed console login attempts (Count: $unique_accounts$) against users from IP Address - $src$'
    risk_objects:
        - field: tried_accounts
          type: user
          score: 20
    threat_objects:
        - field: src
          type: ip_address
tags:
    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
    security_domain: threat
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1110.003/gcp_gws_multiple_login_failure/gws_login.json
          source: gws_login
          sourcetype: gws:reports:login