M365 Copilot Failed Authentication Patterns

name: M365 Copilot Failed Authentication Patterns
id: 0ae94cdd-021a-4a62-a96d-9cec90b61530
version: 3
date: '2026-03-10'
author: Rod Soto
status: production
type: Anomaly
description: Detects M365 Copilot users with failed authentication attempts, MFA failures, or multi-location access patterns indicating potential credential attacks or account compromise. The detection aggregates M365 Copilot Graph API authentication events per user, calculating metrics like distinct cities/countries accessed, unique IP addresses and browsers, failed login attempts (status containing "fail" or "error"), and MFA failures (error code 50074). Users are flagged when they access Copilot from multiple cities (cities_count > 1), experience any authentication failures (failed_attempts > 0), or encounter MFA errors (mfa_failures > 0), which are indicators of credential stuffing, brute force attacks, or compromised accounts attempting to bypass multi-factor authentication.
search: |-
    `m365_copilot_graph_api` (appDisplayName="*Copilot*" OR appDisplayName="M365ChatClient" OR appDisplayName="OfficeAIAppChatCopilot")
      | eval user = userPrincipalName
      | stats count as events, dc(location.city) as cities_count, values(location.city) as city_list, dc(location.countryOrRegion) as countries_count, values(location.countryOrRegion) as country_list, dc(ipAddress) as ip_count, values(ipAddress) as ip_addresses, sum(eval(if(match(status, "(?i)fail
      | error"), 1, 0))) as failed_attempts, sum(eval(if(match(_raw, "50074"), 1, 0))) as mfa_failures, dc(deviceDetail.browser) as browser_count, values(deviceDetail.browser) as browsers_used, min(_time) as first_seen, max(_time) as last_seen by user
      | eval first_seen = strftime(first_seen, "%Y-%m-%d %H:%M:%S")
      | eval last_seen = strftime(last_seen, "%Y-%m-%d %H:%M:%S")
      | where cities_count > 1 OR failed_attempts > 0 OR mfa_failures > 0
      | sort -mfa_failures, -failed_attempts, -countries_count
      | `m365_copilot_failed_authentication_patterns_filter`
data_source:
    - M365 Copilot Graph API
how_to_implement: This detection requires ingesting M365 Copilot access logs via the Splunk Add-on for Microsoft Office 365. Configure the add-on to collect Azure AD Sign-in logs (AuditLogs.SignIns) through the Graph API data input. Ensure proper authentication and permissions are configured to access sign-in audit logs. The `m365_copilot_graph_api` macro should be defined to filter for sourcetype o365:graph:api data containing Copilot application activity.
known_false_positives: Legitimate users experiencing network connectivity issues, traveling employees with intermittent VPN connections, users in regions with unstable internet infrastructure, or password reset activities during business travel may trigger false positives.
references:
    - https://www.splunk.com/en_us/blog/artificial-intelligence/m365-copilot-log-analysis-splunk.html
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="$user$" | where _time >= relative_time(now(), "-168h@h") | 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 $user$ exhibited suspicious M365 Copilot authentication patterns with $failed_attempts$ failed login attempts, $mfa_failures$ MFA failures, and access from $cities_count$ different locations, indicating potential credential compromise or brute force attack.
    risk_objects:
        - field: user
          type: user
          score: 20
    threat_objects: []
tags:
    analytic_story:
        - Suspicious Microsoft 365 Copilot Activities
    asset_type: Web Application
    mitre_attack_id:
        - T1110
    product:
        - Splunk Enterprise
        - Splunk Enterprise Security
        - Splunk Cloud
    security_domain: endpoint
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/m365_copilot/m365_copilot_access.log
          sourcetype: "o365:graph:api"
          source: "AuditLogs.SignIns"