SCS-C03 Exam Dumps - Amazon Web Services AWS Certified Specialty Questions and Answers

EC2 Instance Connect can performserver/host authenticity checksby validating the instance’s SSHhost keyagainst atrusted host keyssource. When you rotate the instance’s host keys, the host presents anewfingerprint. If the trusted host keys source still contains theoldhost key, connections that enforce host key verification will fail with ahost key validationerror. The fix is to update the trusted host key record so the new host key fingerprint is recognized as valid. Therefore, the correct action is toupload the new host keyto the trusted host keys database used for EC2 Instance Connect host key verification.

Option A is unrelated: AWS KMS does not store or manage SSH host keys for EC2 Instance Connect validation. Option C is for AWS Systems Manager managed instances and has no effect on SSH host key validation. Option D rotatesuser/client authentication keys(SSH key pair used to log in) but does not resolve a failure that occurs specifically because theserver host keychanged and is no longer trusted. Updating the trusted host keys database restores the expected trust chain and allows Instance Connect to work again with the rotated host keys.

GuardDuty’s DNS-related detections depend on GuardDuty being able to observeDNS query behaviorthrough AWS-provided DNS resolution paths in the VPC. If a VPC is configured to use acustom DNS resolvervia DHCP options (for example, an OpenDNS resolver) instead of the AmazonProvidedDNS resolver, DNS queries may bypass the visibility path GuardDuty relies on for DNS analysis and pattern detection. In that case, the test traffic (queries to example.com) might not be evaluated by GuardDuty’s DNS finding logic, so no DNS finding is generated—and therefore nothing is forwarded into Security Hub.

Option A is incorrect because VPC flow logs are not a prerequisite for GuardDuty to produce DNS findings; GuardDuty uses native telemetry sources and does not require customer-managed flow logs to be enabled. Option D is irrelevant because the company operates in a single Region, and cross-Region aggregation would not be required for the delegated administrator to see findings from the same Region. Option C is less likely given the setup explicitly states GuardDuty and Security Hub are automatically enabled across accounts; also, even if enabled, the specific lack of a DNS finding points to DNS visibility/configuration rather than a downstream integration toggle.

AWS WAF provides managed and custom rules that can immediately mitigate common web exploits such as SQL injection without modifying application code. According to AWS Certified Security – Specialty documentation, placing AWS WAF in front of an Application Load Balancer is a recommended rapid-response control for legacy applications with known vulnerabilities.

Creating an ALB in front of the existing EC2 instances allows seamless traffic migration. AWS WAF SQL injection rules can be deployed and tested without downtime. Updating Route 53 to point to the ALB preserves normal operations. Restricting EC2 security groups afterward prevents bypassing the WAF.

Option B introduces CloudFront changes and single-origin testing, increasing complexity. Option C cannot be completed within 24 hours and risks downtime. Option D is invalid because AWS WAF cannot be attached directly to EC2 instances.

Referenced AWS Specialty Documents:

AWS Certified Security – Specialty Official Study Guide

AWS WAF Web ACL Architecture

AWS Application Load Balancer Security

The threat is client ID manipulation to break authorization boundaries. The strongest control is tobind the MQTT client identity to the authenticated device identity(the Thing) rather than trusting arbitrary client IDs provided by the client. Using theThing name as the client ID(Option A) removes ambiguity and makes the identifier predictable and tied to a registered identity.

On the authorization side, AWS IoT Core policies can use policy variables. Allowing iot:Connect only when the resource matches client/${iot:Connection.Thing.ThingName} (Option E) ensures the connection is permittedonlyif the client ID exactly equals the authenticated Thing name from the TLS certificate/Thing principal context. This prevents attackers from injecting special characters or choosing a different client ID to escalate access, because the policy evaluation ties the allowed client resource to the Thing identity, not the attacker-controlled string.

Option D is weaker because it effectively allows whatever client ID is presented (it matches the same value the client supplies), so it does not prevent crafted client IDs from being used. Option C is unrelated to the described MQTT connect authorization (and references an action not aligned with the scenario). Option B is an application-side check and can be bypassed by a malicious client; enforcement must be at AWS IoT Core policy level.

Amazon S3 pre-signed URLs grant temporary access based on the permissions of the principal that generates them. AWS Certified Security – Specialty documentation explains that fine-grained authorization can be enforced by combining pre-signed URLs with IAM policy conditions.

By tagging each invoice object with a client identifier and adding a condition to the EC2 instance role policy using s3:ResourceTag/ClientId, the role can generate pre-signed URLs only for objects associated with a specific client. This ensures that each client can access only their own invoices, even though the URLs are temporary and unauthenticated.

Option A over-permissions clients. Option C is unnecessary because instance profiles already use temporary credentials. Option D violates AWS best practices by using long-term credentials.

AWS recommends resource tagging with IAM policy conditions for scalable, secure access control.

Referenced AWS Specialty Documents:

AWS Certified Security – Specialty Official Study Guide

Amazon S3 Pre-Signed URLs

IAM Policy Conditions and Resource Tags

To restrict activity to a single Region in an OU using an SCP, the standard pattern is an explicitDenyfor requests madeoutsidethe allowed Region, while carving out exceptions forglobal servicesthat do not use aws:RequestedRegion in the same way (or that must remain usable regardless of Region). This is done withEffect: Deny, aConditionusing StringNotEquals on aws:RequestedRegion for the allowed Region (here, eu-west-1), andNotActionlisting the global services that should remain available.

This works because SCPs act asguardrails: an explicit Deny in an SCP overrides IAM Allow in member accounts, ensuring the restriction applies consistently to all existing and future accounts placed in the OU. The StringNotEquals condition ensures the deny triggers for any Region other than eu-west-1. The NotAction exception list ensures that the specified global services are not blocked by this deny statement.

Option A is wrong because StringEquals would deny actionsineu-west-1 rather than outside it. Options B and D useAllowstatements, which do not enforce “only this Region” safely in SCPs unless combined with a comprehensive deny strategy; they would not reliably restrict all other services/regions. Therefore, option C is the correct SCP structure.

A rate-based rule in AWS WAF is designed to quickly mitigate spikes and potential layer 7 floods bytracking request rates per originating IPand temporarily blocking (or counting/challenging, depending on configuration) IPs that exceed a defined threshold within a 5-minute rolling window. In this scenario, the malicious traffic is distributed acrosshundreds of IPsin two countries, and the application still needs to remain available globally for legitimate users. A rate-based rule provides fast, targeted throttling that reduces abusive request patterns without permanently blocking entire geographies. This aligns with “quickly limit” while minimizing collateral impact.

Blocking both countries with a geo match rule (Option B) would likely block legitimate users located in those countries, which violates the requirement. Security groups (Options C and D) cannot natively enforcegeographicfiltering, and they are not well suited for large, rapidly changing sets of public source IPs at the application layer. Additionally, WAF operates at layer 7 with richer matching (rate limiting, URI/header patterns, bot controls), which is the appropriate control point when the ALB already has a web ACL associated. Therefore, implementing an AWS WAFrate-basedrule is the most effective and least disruptive immediate mitigation.

The most secure and AWS-recommended pattern for cross-account access is to create anIAM role in the target account (production)and allow trusted principals from the source account (developer) toassume the roleby using AWS STS. This avoids long-term credentials in the production account, supports short-lived session credentials, and enables strong controls such as MFA requirements, session duration limits, and precise least-privilege permissions attached to the role. It also centralizes ownership of production permissions in the production account, which is important for separation of duties and governance.

Option A is insecure because it requires password sharing and uses a long-lived IAM user credential, which is against AWS best practices. Option C is also poor because it relies on a long-lived IAM user in the production account and encourages credential sharing/duplication. Option B places the role in the developer account; while you can attach permissions there, access to production resources is governed by the production account. The standard approach is a production-account role with a trust policy that names the developer account principals (or a role) as allowed to assume it. Therefore, Option D is the most secure solution.

AWS Config is a fully managed service that providescontinuous monitoring and evaluation of AWS resource configurationsagainst desired configuration baselines. According to the AWS Certified Security – Specialty Official Study Guide, AWS Config is the primary service used totrack configuration changes, evaluate compliance in near real time, and display compliance statesfor individual AWS resources.

AWS Config providesmanaged rulesthat directly map to the listed Aurora MySQL security requirements, including encryption at rest, public accessibility, deletion protection, and log exports to CloudWatch Logs. These managed rules continuously evaluate resources and mark them as compliant or noncompliant whenever a configuration change occurs.

The AWS Config dashboard enables security engineers to viewper-resource and per-rule compliance states at any point in time, satisfying the requirement to display compliance status for each part of the policy.

AWS Audit Manager (Option A) is designed for audit evidence collection and reporting, not continuous monitoring. AWS Security Hub (Option C) aggregates findings from other services but relies on AWS Config for configuration compliance data. Option D introduces unnecessary custom logic and does not provide a native compliance dashboard.

AWS documentation explicitly identifiesAWS Config as the authoritative service for continuous compliance monitoring and visibility.

AWS Certified Security – Specialty Official Study Guide

AWS Config Developer Guide

Amazon Aurora Security Best Practices

AWS Well-Architected Framework – Security Pillar

AWS WAF supports logging of detailed HTTP request information, including source IP addresses, request URIs, headers, and rule evaluation results. According to the AWS Certified Security – Specialty documentation,Amazon S3 combined with Amazon Athenais the recommended and most cost-effective solution for ad hoc and forensic analysis of AWS WAF logs.

By configuring AWS WAF to deliver logs to Amazon S3 and usingAthena with partition projection, the security engineer can efficiently query large volumes of log data without maintaining partitions manually. This enables rapid identification of application-layer attacks such as SQL injection, cross-site scripting, and bot activity.

Options A and D are incorrect because AWS WAF logs are not delivered to CloudTrail. Option B is invalid because OpenSearch cannot directly query data stored in S3 without ingestion or additional tooling.

AWS documentation highlightsS3 + Athenaas a best practice for scalable, serverless analysis of AWS WAF logs.

AWS Certified Security – Specialty Official Study Guide

AWS WAF Logging Documentation

Amazon Athena Best Practices