splunk_escuTTP

O365 High Number Of Failed Authentications for User

The following analytic identifies an O365 account experiencing more than 20 failed authentication attempts within 5 minutes. It uses O365 Unified Audit Logs, specifically "UserLoginFailed" events, to monitor and flag accounts exceeding this threshold. This activity is significant as it may indicate a brute force attack or password guessing attempt. If confirmed malicious, an attacker could gain unauthorized access to the O365 environment, potentially compromising sensitive emails, documents, and other data. Prompt investigation and action are crucial to prevent unauthorized access and data breaches.

MITRE ATT&CK

T1110.001

Detection Query

`o365_management_activity` Operation=UserLoginFailed record_type=AzureActiveDirectoryStsLogon Workload=AzureActiveDirectory
  | bucket span=5m _time
  | fillnull
  | stats dc(_raw) AS failed_attempts values(src_ip) as src
    BY signature user _time
       dest vendor_account vendor_product
  | where failed_attempts > 10
  | `o365_high_number_of_failed_authentications_for_user_filter`

Author

Mauricio Velazco, Splunk

Created

2026-03-10

Data Sources

O365 UserLoginFailed

References

Tags

Office 365 Account Takeover

Raw Content

name: O365 High Number Of Failed Authentications for User
id: 31641378-2fa9-42b1-948e-25e281cb98f7
version: 10
date: '2026-03-10'
author: Mauricio Velazco, Splunk
status: production
type: TTP
data_source:
    - O365 UserLoginFailed
description: The following analytic identifies an O365 account experiencing more than 20 failed authentication attempts within 5 minutes. It uses O365 Unified Audit Logs, specifically "UserLoginFailed" events, to monitor and flag accounts exceeding this threshold. This activity is significant as it may indicate a brute force attack or password guessing attempt. If confirmed malicious, an attacker could gain unauthorized access to the O365 environment, potentially compromising sensitive emails, documents, and other data. Prompt investigation and action are crucial to prevent unauthorized access and data breaches.
search: |-
    `o365_management_activity` Operation=UserLoginFailed record_type=AzureActiveDirectoryStsLogon Workload=AzureActiveDirectory
      | bucket span=5m _time
      | fillnull
      | stats dc(_raw) AS failed_attempts values(src_ip) as src
        BY signature user _time
           dest vendor_account vendor_product
      | where failed_attempts > 10
      | `o365_high_number_of_failed_authentications_for_user_filter`
how_to_implement: You must install the Splunk Microsoft Office 365 Add-on and ingest Office 365 management activity events.
known_false_positives: Although unusual, users who have lost their passwords may trigger this detection. Filter as needed.
references:
    - https://attack.mitre.org/techniques/T1110/
    - https://attack.mitre.org/techniques/T1110/001/
drilldown_searches:
    - name: View the detection results for - "$user$"
      search: '%original_detection_search% | search  user = "$user$"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
    - name: View risk events for the last 7 days for - "$user$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$user$") 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: User $user$ failed to authenticate more than 10 times in the span of 5 minutes.
    risk_objects:
        - field: user
          type: user
          score: 50
    threat_objects:
        - field: src
          type: ip_address
tags:
    analytic_story:
        - Office 365 Account Takeover
    asset_type: O365 Tenant
    mitre_attack_id:
        - T1110.001
    product:
        - Splunk Enterprise
        - Splunk Enterprise Security
        - Splunk Cloud
    security_domain: identity
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1110.001/o365_high_number_authentications_for_user/o365_high_number_authentications_for_user.log
          source: o365:management:activity
          sourcetype: o365:management:activity