Amazon Web Services Updated SCS-C03 Exam Questions and Answers by laurie

Comprehensive and Detailed 100to 150 words of Explanation From AWS Certified Security – Specialty topics:

AWS WAF rate-based rules are the fastest native mitigation for high-frequency bot or brute-force request patterns against an ALB. A rate-based rule counts requests by aggregation key, commonly source IP address, during an evaluation window and can block clients that exceed the configured threshold. Creating the rule directly in a web ACL associated with the ALB is faster and cleaner than building custom Lambda log-processing logic. ALB listener rules can match known source IPs and paths, but they do not provide automatic rate tracking for distributed brute-force behavior. Creating a reusable rule group is possible, but it adds unnecessary setup when the immediate requirement is fastest mitigation.

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Comprehensive and Detailed 100to 150 words of Explanation From AWS Certified Security – Specialty topics:

Session Manager requires the target EC2 instance to be a managed node, which means Systems Manager Agent must be installed and running, and the instance profile must grant permissions for Systems Manager communication. In a private VPC with no internet connectivity, the instances need private connectivity to Systems Manager service endpoints through VPC interface endpoints. Depending on configuration, endpoints commonly include Systems Manager, EC2 messages, and Systems Manager messages; EC2 endpoint access can also be needed for related management operations. A NAT gateway would create internet-bound egress and conflicts with the private VPC requirement. A transit gateway does not provide AWS Systems Manager service connectivity by itself. Preventing SSH key pair creation is not required for Session Manager operation.

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To achieve true separation of duties, the company needs a design whereS3 access alone is not sufficientto read plaintext data.SSE-KMS with a customer managed KMS keyprovides that separation because successful object reads require both: (1) S3 permissions to read the object and (2) permission to use the KMS key to decrypt it. This enables the operations team to manage bucket and object permissions while the security team independently controls key usage through theKMS key policy(and grants). If either team misconfigures only their part, the data is still protected: an overly permissive bucket policy won’t expose plaintext unless KMS decrypt is also allowed; similarly, KMS permissions alone are not sufficient without S3 read access.

Option B also adds a bucket policy requirement enforcingSSE-KMSso objects are consistently protected with the customer managed key. SSE-S3 options (A and C) do not provide the same separation because S3 manages the keys and decryption is not independently controlled by a separate team via KMS policies. Option D is invalid because SSE-C uses customer-provided keys that are supplied with each request and are not stored/managed in KMS as described. Therefore, SSE-KMS with customer managed keys plus restrictive key policy is the correct solution.

AWS KMS key policies can restrict how and when a key is used by applyingconditions such as kms:ViaService, which limits usage to requests that originate from a specific AWS service. According to the AWS Certified Security – Specialty Official Study Guide and AWS KMS documentation, the kms:ViaService condition is evaluated against the service that calls KMS on behalf of the principal.

Using StringEquals with kms:ViaService restricts usage toexactly one service endpoint. However, AWS services can invoke KMS throughservice variants, internal endpoints, or additional service integrations. When StringEquals is used, these variations can unintentionally bypass the condition, allowing the key to be used by other services through different internal service paths.

Changing the condition operator from StringEquals to StringLike ensures thatonly EC2-related service callsthat match the intended service pattern are allowed, while still preventing use by unrelated AWS services. This aligns with AWS guidance to use StringLike when service invocation patterns may vary.

Option B is incorrect because the root principal statement is required to retain administrative control over the key. Option C is invalid because changing Regions does not address unauthorized service usage. Option D does not restrict key usage and does not mitigate the issue.

AWS documentation explicitly recommendstightening condition operatorsin KMS key policies to prevent unintended service access while maintaining required functionality.

AWS Certified Security – Specialty Official Study Guide

AWS Key Management Service Developer Guide

AWS KMS Key Policy Best Practices