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2.1.4 Ensure that S3 is configured with 'Block Public Access' enabled

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Information

Amazon S3 provides Block public access (bucket settings) and Block public access (account settings) to help you manage public access to Amazon S3 resources. By default, S3 buckets and objects are created with public access disabled. However, an IAM principal with sufficient S3 permissions can enable public access at the bucket and/or object level. While enabled, Block public access (bucket settings) prevents an individual bucket and its contained objects from becoming publicly accessible. Similarly, Block public access (account settings) prevents all buckets and their contained objects from becoming publicly accessible across the entire account.

Amazon S3 Block public access (bucket settings) prevents the accidental or malicious public exposure of data contained within the respective bucket(s).

Amazon S3 Block public access (account settings) prevents the accidental or malicious public exposure of data contained within all buckets of the respective AWS account.

Whether to block public access to all or some buckets is an organizational decision that should be based on data sensitivity, least privilege, and use case.

Solution

If utilizing Block Public Access (bucket settings)

From Console:

 - Login to the AWS Management Console and open the Amazon S3 console using

https://console.aws.amazon.com/s3/

.
 - Select the check box next to a bucket.
 - Click 'Edit public access settings'.
 - Click 'Block all public access'
 - Repeat for all the buckets in your AWS account that contain sensitive data.

From Command Line:

 - List all of the S3 buckets:

aws s3 ls <xhtml:ol start="2"> - Enable Block Public Access on a specific bucket:

aws s3api put-public-access-block --bucket <bucket-name> --public-access-block-configuration "BlockPublicAcls=true,IgnorePublicAcls=true,BlockPublicPolicy=true,RestrictPublicBuckets=true"

If utilizing Block Public Access (account settings)

From Console:

If the output reads true for the separate configuration settings, then Block Public Access is enabled on the account.

 - Login to the AWS Management Console and open the Amazon S3 console using

https://console.aws.amazon.com/s3/

.
 - Click Block Public Access (account settings)
 - Click Edit to change the block public access settings for all the buckets in your AWS account.
 - Update the settings and click Save For details about each setting, pause on the i icons.
 - When you're asked for confirmation, enter confirm Then click Confirm to save your changes.

From Command Line:

To enable Block Public Access for this account, run the following command:

aws s3control put-public-access-block
--public-access-block-configuration BlockPublicAcls=true, IgnorePublicAcls=true, BlockPublicPolicy=true, RestrictPublicBuckets=true
--account-id <account-id>

Impact:

When you apply Block Public Access settings to an account, the settings apply to all AWS regions globally. The settings may not take effect in all regions immediately or simultaneously, but they will eventually propagate to all regions.

See Also

https://workbench.cisecurity.org/benchmarks/20495

Item Details

References: CSCv7|14.6

Plugin: amazon_aws

Control ID: abf9eb881d47f0ca8eedbe14dbfe4c49b72eb94dbee39d8b38fecbe3150be5b0