Amazon S3 (Simple Storage Service) Public Access Block is a feature provided by Amazon Web Services (AWS) that helps you secure your S3 buckets and objects against unauthorized public access.
By default, when you create an S3 bucket, it is set to be private, meaning only the bucket owner can access its content.
However, sometimes, misconfigurations or human errors can lead to unintentional public access, potentially exposing sensitive data to the public.
To prevent such unintended access, AWS introduced the Public Access Block feature. It allows you to enforce restrictions on public access at the bucket and object levels, helping you maintain data privacy and security.
Note: Starting from April 2023 all public access to new buckets disabled by default: "Amazon S3 now automatically enables S3 Block Public Access and disables S3 access control lists (ACLs) for all new S3 buckets in all AWS Regions."
It means that by default, you are unable to make files public in buckets created after April 2023. If you would like to enable the possibility of making files public, please follow these instructions.
1. Select the bucket you want to manage the Public Access Block Configuration for and click Buckets, Public Access Block Configuration:Click Buckets, Public Access Block Configuration or use the Ctrl+B keyboard shortcut
The Public Access Block Configuration dialog will open:Public Access Block Configuration dialog
Enable public access block configuration for [bucket] - Turn this check-box on to enable public access block configuration for selected bucket.
Block public ACL - Specifies whether Amazon S3 should block public access control lists (ACLs) for this bucket and objects in this bucket. Turning this option ON causes the following behavior:
- PUT Bucket ACL and PUT Object ACL calls fail if the specified ACL is public.
- PUT Object calls fail if the request includes a public ACL.
- PUT Bucket calls fail if the request includes a public ACL.
- Enabling this setting doesn't affect existing policies or ACLs.
Block public policy - Specifies whether Amazon S3 should block public bucket policies for this bucket. Turning this option ON causes Amazon S3 to reject calls to PUT Bucket policy if the specified bucket policy allows public access. Enabling this setting doesn't affect existing bucket policies.
Ignore public ACLs - Specifies whether Amazon S3 should ignore public ACLs for this bucket and objects in this bucket. Turning this option ON causes Amazon S3 to ignore all public ACLs on this bucket and objects in this bucket. Enabling this setting doesn't affect the persistence of any existing ACLs and doesn't prevent new public ACLs from being set.
Restrict public buckets - Specifies whether Amazon S3 should restrict public bucket policies for this bucket. Turning this option ON restricts access to this bucket to only AWS service principals and authorized users within this account if the bucket has a public policy. Enabling this setting doesn't affect previously stored bucket policies, except that public and cross-account access within any public bucket policy, including non-public delegation to specific accounts, is blocked.
2. Configure Public Access Block Configuration and click OK to save changes and close the dialog.
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