Rule: S3 Public Access Blocked at Account Level
This rule ensures S3 public access is disabled at the account level to enhance security.
| Rule | S3 public access should be blocked at account level |
| Framework | NIST 800-171 Revision 2 |
| Severity | ✔ Medium |
Rule Description
S3 public access should be blocked at the account level for NIST 800-171 Revision 2 compliance. This rule ensures the security of sensitive data stored in Amazon S3 buckets by preventing unauthorized access from the public internet.
Reason for the Rule
NIST 800-171 Revision 2 provides guidelines for protecting the confidentiality of Controlled Unclassified Information (CUI). By blocking public access to S3 buckets at the account level, organizations can enforce stricter controls and reduce the risk of data exposure or unauthorized access.
Troubleshooting Steps (if applicable)
If S3 public access is still allowed, follow the troubleshooting steps below:
- 1.
Validate the account permissions: Check if you have the necessary permissions to modify S3 bucket policies and access control settings at the account level.
- 2.
Verify bucket policies: Ensure that the bucket policies for all S3 buckets are not granting public access. Look for any policies that allow "Principal" or "AWS: *". These should be removed or modified to restrict access appropriately.
- 3.
Check block public access settings: Confirm that the block public access settings are enabled at the account level. This can be done by navigating to the Amazon S3 console, selecting the account name, and then checking the "Block public access" settings.
- 4.
Audit bucket access logs: Review the S3 bucket access logs to identify any unauthorized access attempts or configurations that may be allowing public access. This information can help identify the root cause of the public access issue.
- 5.
Validate IAM policies: Ensure that the IAM policies associated with users, groups, and roles are not granting excessive permissions that could override the block public access settings. Review and update these policies as necessary.
- 6.
Verify bucket permissions: Check the permissions of each S3 bucket individually to ensure that public access is explicitly denied.
- 7.
Test public access restrictions: Try accessing the S3 buckets using different methods (e.g., direct URL access, SDKs, or command-line tools) to confirm that public access is indeed blocked.
Necessary Codes (if applicable)
There are no specific codes for this rule. The management of S3 public access at the account level can be done through the AWS Management Console or programmatically using AWS CLI or SDKs.
Step-by-Step Guide for Remediation
Follow the steps below to block S3 public access at the account level:
- 1.
Log in to the AWS Management Console with administrative privileges.
- 2.
Navigate to the Amazon S3 service.
- 3.
Select the account name or ID in the top-right corner of the S3 dashboard.
- 4.
In the account settings, click on the "Block public access" option.
- 5.
Ensure that all four block public access settings are enabled: a. Block new public ACLs and uploading public objects (Recommended) b. Remove public access granted through public ACLs (Recommended) c. Block new public bucket policies (Recommended) d. Block public and cross-account access if bucket has public policies (Recommended)
- 6.
Save the changes and verify that the block public access settings are successfully applied.
- 7.
Review the bucket policies for each S3 bucket in your account to ensure that they do not grant public access. Modify or remove any policies that allow public access.
- 8.
Validate the IAM policies associated with users, groups, and roles to guarantee they do not grant excessive permissions that could bypass the block public access settings.
- 9.
Monitor access logs for any unauthorized access attempts and regularly review bucket permissions to maintain the security of your S3 buckets.
- 10.
Test the public access restrictions by attempting to access the S3 buckets using different methods to verify that public access is blocked.
By following these steps, you can block S3 public access at the account level and maintain compliance with NIST 800-171 Revision 2 requirements.