AWS Multiple Failed MFA Requests For User

name: AWS Multiple Failed MFA Requests For User
id: 1fece617-e614-4329-9e61-3ba228c0f353
version: 9
date: '2026-03-10'
author: Bhavin Patel
status: production
type: Anomaly
description: The following analytic identifies multiple failed multi-factor authentication (MFA) requests to an AWS Console for a single user. It leverages AWS CloudTrail logs, specifically the `additionalEventData` field, to detect more than 10 failed MFA prompts within 5 minutes. This activity is significant as it may indicate an adversary attempting to bypass MFA by bombarding the user with repeated authentication requests. If confirmed malicious, this could lead to unauthorized access to the AWS environment, potentially compromising sensitive data and resources.
data_source:
    - AWS CloudTrail ConsoleLogin
search: |-
    `cloudtrail` eventName= ConsoleLogin "additionalEventData.MFAUsed"=Yes errorMessage="Failed authentication"
      | bucket span=5m _time
      | rename user_name as user
      | stats dc(_raw) as mfa_prompts min(_time) as firstTime max(_time) as lastTime values(user_agent) as user_agent values(src) as src values(dest) as dest
        BY _time user signature
           vendor_account vendor_region vendor_product
           errorMessage
      | where mfa_prompts > 10
      | `security_content_ctime(firstTime)`
      | `security_content_ctime(lastTime)`
      | `aws_multiple_failed_mfa_requests_for_user_filter`
how_to_implement: The Splunk AWS Add-on is required to utilize this data. The search requires AWS CloudTrail logs.
known_false_positives: Multiple Failed MFA requests may also be a sign of authentication or application issues. Filter as needed.
references:
    - https://attack.mitre.org/techniques/T1621/
    - https://aws.amazon.com/what-is/mfa/
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 $user$ is seen to have high number of MFA prompt failures within a short period of time.
    risk_objects:
        - field: user
          type: user
          score: 20
    threat_objects:
        - field: src
          type: ip_address
tags:
    analytic_story:
        - AWS Identity and Access Management Account Takeover
    asset_type: AWS Account
    mitre_attack_id:
        - T1586.003
        - T1621
    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/T1621/aws_failed_mfa/cloudtrail.json
          sourcetype: aws:cloudtrail
          source: aws_cloudtrail