# 4.8 Ensure S3 bucket policy changes are monitored (Manual) - Source: https://support.icompaas.com/support/solutions/articles/62000234262-4-8-ensure-s3-bucket-policy-changes-are-monitored-manual- - Section: [Solutions](https://support.icompaas.com/support/solutions) › [CIS Amazon Web Services Foundations Benchmark v5.0.0](https://support.icompaas.com/support/solutions/62000112684) › [CIS AWS Benchmarks](https://support.icompaas.com/support/solutions/folders/62000169233) - Last updated: 2026-05-29 - Publisher: iCompaas, Inc. (https://www.icompaas.com) #### Profile Applicability - **Level 1** #### Description: Amazon S3 bucket policies are crucial for controlling access to data stored within S3 buckets. These policies define the actions that can be performed on the objects in the bucket and who can perform those actions. Monitoring changes to S3 bucket policies ensures that any modifications to access control settings are captured and reviewed, preventing unauthorized access or misconfigurations. By monitoring changes to S3 bucket policies, organizations can maintain visibility into who is able to access sensitive data and ensure compliance with data security policies. #### Rationale: Changes to S3 bucket policies can significantly impact the security and accessibility of data. For example: - Unauthorized changes to bucket policies can expose sensitive data to the public or unauthorized users. - Misconfigured policies can result in unintended access to or modification of stored objects. Monitoring S3 bucket policy changes helps ensure that all modifications are legitimate and that access control remains secure, reducing the risk of data breaches and compliance violations. #### Impact: Failure to monitor S3 bucket policy changes can result in: - Exposure of sensitive data to unauthorized users - Unintended access or modification of data due to misconfigured policies - Violations of compliance requirements (e.g., GDPR, HIPAA) By ensuring that bucket policy changes are monitored, organizations can quickly identify and correct issues before they lead to a security incident. #### Default Value: By default, S3 bucket policy changes are not automatically monitored. However, changes can be tracked using AWS CloudTrail and AWS Config, which allow you to monitor and log changes made to S3 bucket policies. #### Pre-Requisites: - AWS CLI installed and configured - IAM permissions: - s3:GetBucketPolicy - cloudtrail:LookupEvents - config:DescribeConfigurationRecorder - CloudTrail and AWS Config should be enabled in all AWS regions for monitoring changes #### Remediation: ##### Test Plan: Using AWS Console: 1. Go to the [CloudTrail Console](https://console.aws.amazon.com/cloudtrail/). 2. Ensure that Management Events are enabled to capture changes to S3 bucket policies. 3. Navigate to the [AWS Config Console](https://console.aws.amazon.com/config/) and verify that the Configuration Recorder is active and tracking changes to S3 bucket configurations. 4. Review S3 bucket policy changes in CloudTrail and AWS Config to ensure proper logging. Using AWS CLI: aws cloudtrail describe-trails --query "trailList\[?Name==''\].{Name:Name, S3BucketName:S3BucketName}" --output table To verify if AWS Config is tracking S3 bucket changes: aws configservice describe-configuration-recorders --query "ConfigurationRecorders\[?recordingGroup.allSupported==\`true\`\].{Name:name, RecordingGroup:recordingGroup}" --output table ##### Implementation Plan: Using AWS Console: 1. Enable CloudTrail logging for S3 bucket policy changes: - Go to the [CloudTrail Console](https://console.aws.amazon.com/cloudtrail/). - Ensure Management Events are enabled to log S3 bucket policy changes. - Create or update a trail to log events in All Regions. 2. Enable AWS Config to monitor S3 bucket configurations: - Go to the [AWS Config Console](https://console.aws.amazon.com/config/) - Enable the Configuration Recorder and ensure that S3 bucket configurations (including bucket policies) are included in the recording configuration. Using AWS CLI: 1. Verify CloudTrail is logging S3 bucket policy changes: aws cloudtrail describe-trails --query "trailList\[?Name==''\].{Name:Name, S3BucketName:S3BucketName}" --output table 2. Enable AWS Config to track S3 bucket policies: aws configservice record-configuration-changes --configuration-recorder-name --include-configuration-item-types "AWS::S3::Bucket" #### Backout Plan: Using AWS Console: 1. If monitoring S3 bucket policy changes causes excessive logging or performance issues: - Go to the [CloudTrail Console](https://console.aws.amazon.com/cloudtrail/). - Disable logging for S3 bucket policy changes or adjust the event capture settings to limit the types of logged events. 2. Modify AWS Config settings to exclude S3 bucket policies from being recorded or reduce the number of resources being tracked. - In the [AWS Config Console](https://console.aws.amazon.com/config/), adjust the Configuration Recorder to exclude S3 buckets or reduce resource tracking. Using AWS CLI: 1. If excessive logging or performance issues occur: - Temporarily stop the configuration recorder: aws configservice stop-configuration-recorder --configuration-recorder-name 2. To modify the scope of tracked resources: - Update the configuration recorder settings to reduce the number of S3 bucket configurations being tracked: aws configservice put-configuration-recorder --configuration-recorder-name --recording-group 3. Re-enable monitoring once issues are resolved: aws configservice start-configuration-recorder --configuration-recorder-name #### References: - [AWS CloudTrail Documentation](https://docs.aws.amazon.com/awscloudtrail/latest/userguide/cloudtrail-user-guide.html) - [AWS Config Documentation](https://docs.aws.amazon.com/config/latest/developerguide/) - [AWS S3 Bucket Policies Documentation](https://docs.aws.amazon.com/AmazonS3/latest/dev/UsingBucketPolicies.html) #### CIS Controls Mapping:

CIS Control Version

Control ID

Control Description

CIS v8

4.9

Perform Continuous Security Monitoring and Incident Detection

CIS v7

6.3

Monitor Security Configurations for Compliance

CIS v7

5.2

Securely Manage and Monitor Cloud Accounts and Services

## Related compliance guidance - [SOC 2 compliance: a practical implementation guide for cloud-native SaaS teams](https://support.icompaas.com/compliance/soc-2-trust-services-criteria): Configuration checks like this one are the technical half of a SOC 2 / ISO 27001 programme — the guide shows where they fit, what else an auditor expects, and how to evidence them. - [ISO/IEC 27001:2022 compliance: a practical implementation guide](https://support.icompaas.com/compliance/iso-27001-2022): ISO 27001 Annex A.8 (technological controls) is where cloud hardening evidence lands; the guide shows how to run the ISMS around it.