SCS-C03 Leak Questions

SSE-S3 uses AWS-managed keys and does not provide customer control. AWS Certified Security – Specialty documentation states that SSE-KMS with customer managed keys allows full control, auditing, and key rotation. The security engineer must first create a customer managed KMS key, then update the bucket to use SSE-KMS. Existing objects must be re-encrypted to ensure compliance.

SSE-C requires the application to manage keys, increasing complexity and risk. AWS managed keys do not meet the requirement for customer-controlled encryption.

Referenced AWS Specialty Documents:

AWS Certified Security – Specialty Official Study Guide

Amazon S3 Encryption Options

AWS KMS Customer Managed Keys

Amazon Macie is the AWS service designed to discover and classify sensitive data in S3. Delegated administration enables centralized visibility across an organization. Security Hub aggregates Macie findings for a single-pane-of-glass view.

Inspector does not scan S3 data. Trusted Advisor is not a sensitive data discovery tool.

Referenced AWS Specialty Documents:

AWS Certified Security – Specialty Official Study Guide

Amazon Macie Multi-Account Architecture

AWS networking best practices require private subnets to access the internet only through NAT gateways located in public subnets. According to the AWS Certified Security – Specialty Study Guide, NAT gateways must be provisioned in public subnets and used as the default route for outbound traffic from private subnets.

Verifying NAT gateways in each Availability Zone ensures high availability and fault tolerance. Updating the private subnet route tables to send 0.0.0.0/0 traffic to the NAT gateway prevents direct internet access while allowing outbound connectivity.

Routing private subnet traffic directly to an internet gateway violates subnet isolation principles. NAT gateways must never be placed in private subnets.

Referenced AWS Specialty Documents:

AWS Certified Security – Specialty Official Study Guide

Amazon VPC Routing and NAT Gateways

AWS Network Segmentation Best Practices

Amazon S3 Block Public Access configured at the AWS account level is the recommended and most effective approach to protect data stored in Amazon S3 while minimizing operational overhead. AWS Security Specialty documentation explains that S3 Block Public Access provides centralized, preventative controls designed to block public access to S3 buckets and objects regardless of individual bucket policies or object-level ACL configurations. When enabled at the account level, these controls automatically apply to all existing and newly created buckets, significantly reducing the risk of accidental exposure caused by misconfigured permissions.

The AWS Certified Security – Specialty Study Guide emphasizes that public access misconfiguration is a leading cause of data leaks in cloud environments. Account-level S3 Block Public Access acts as a guardrail by overriding any attempt to grant public permissions through bucket policies or ACLs. This eliminates the need to manage security settings on a per-bucket or per-object basis, thereby reducing administrative complexity and human error.

Configuring Block Public Access at the object level, as in option B, requires continuous monitoring and manual configuration, which increases operational overhead. Disabling ACLs alone, as described in option C, does not fully prevent public access because bucket policies can still allow public permissions. Using AWS PrivateLink, as in option D, controls network access but does not protect against public exposure through misconfigured S3 policies.

AWS security best practices explicitly recommend enabling S3 Block Public Access at the account level as the primary mechanism for preventing unintended public data exposure with minimal management effort.

Referenced AWS Specialty Documents:

AWS Certified Security – Specialty Official Study Guide

Amazon S3 Security Best Practices Documentation

Amazon S3 Block Public Access Overview

AWS Well-Architected Framework – Security Pillar