AWS Bedrock Invoke Model Access Denied

SPLUNK detection rule by Bhavin Patel, Splunk · Apache-2.0

The following analytic identifies access denied error when attempting to invoke AWS Bedrock models. It leverages AWS CloudTrail logs to detect when a user or service receives an AccessDenied error when calling the InvokeModel API. This activity is significant as it may indicate an adversary attempting to access Bedrock models with insufficient permissions after compromising credentials. If confirmed malicious, this could suggest reconnaissance activities or privilege escalation attempts targeting generative AI resources, potentially leading to data exfiltration or manipulation of model outputs.

name: AWS Bedrock Invoke Model Access Denied
id: c53a8e62-f741-11ee-9f6e-acde48001122
version: 6
creation_date: '2025-03-25'
modification_date: '2026-05-13'
author: Bhavin Patel, Splunk
status: production
type: TTP
description: The following analytic identifies access denied error when attempting to invoke AWS Bedrock models. It leverages AWS CloudTrail logs to detect when a user or service receives an AccessDenied error when calling the InvokeModel API. This activity is significant as it may indicate an adversary attempting to access Bedrock models with insufficient permissions after compromising credentials. If confirmed malicious, this could suggest reconnaissance activities or privilege escalation attempts targeting generative AI resources, potentially leading to data exfiltration or manipulation of model outputs.
data_source:
    - AWS CloudTrail
search: >-
    `cloudtrail` eventSource=bedrock.amazonaws.com eventName=InvokeModel errorCode=AccessDenied
    | rename user_name as user
    | stats count min(_time) as firstTime max(_time) as lastTime values(requestParameters.modelId) as modelIds by src user user_agent vendor_account vendor_product dest signature vendor_region result result_id
    | `security_content_ctime(firstTime)`
    | `security_content_ctime(lastTime)`
    | `aws_bedrock_invoke_model_access_denied_filter`
how_to_implement: The Splunk AWS Add-on is required to utilize this data. The search requires AWS CloudTrail logs with Bedrock service events enabled. You must install and configure the AWS App for Splunk (version 6.0.0 or later) and Splunk Add-on for AWS (version 5.1.0 or later) to collect CloudTrail logs from AWS.
known_false_positives: Legitimate users may encounter access denied errors during permission testing, role transitions, or when service permissions are being reconfigured. Access denials may also happen when automated processes are using outdated credentials or when new Bedrock features are being explored.
references:
    - https://docs.aws.amazon.com/bedrock/latest/APIReference/API_ListFoundationModels.html
    - https://trustoncloud.com/blog/exposing-the-weakness-how-we-identified-a-flaw-in-bedrocks-foundation-model-access-control/
    - https://attack.mitre.org/techniques/T1595/
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 ("$user$") | 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: 7d
      latest_offset: "0"
finding:
    title: User $user$ access denied when attempting to invoke AWS Bedrock models from $src$
    entity:
        field: user
        type: user
        score: 50
threat_objects:
    - field: src
      type: ip_address
analytic_story:
    - AWS Bedrock Security
asset_type: AWS Account
mitre_attack_id:
    - T1078
    - T1550
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: cloud
security_domain: threat
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1087.004/aws_invoke_model_access_denied/cloudtrail.json
          sourcetype: aws:cloudtrail
          source: aws_cloudtrail
      test_type: unit

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