Amazon Web Services SCS-C03 - AWS Certified Security – Specialty

To performcustom validation at sign-upand explicitlyaccept or denyregistrations, Amazon Cognito providesLambda triggers. APre sign-up triggerruns synchronously during the sign-up flow (including the Hosted UI) and can implement custom checks (for example, IP reputation checks, email/domain validation, velocity checks, allow/deny lists, or geo checks using an external service). Based on the trigger logic, the function can allow the sign-up to proceed or reject it, meeting the “custom validation” and “accept/deny” requirement directly.

Because the observed fraud largely originatesoutside France, adding a front-door geographic control reduces unwanted traffic before it reaches Cognito.AWS WAFsupportsGeo matchconditions in a web ACL to allow/deny requests by country, which is a common mitigation for region-scoped applications. Associating a WAF web ACL to protect the Hosted UI endpoint helps block sign-up requests from non-French locations early, reducing fraud attempts and load.

The other options do not meet the requirement: Cognito user pools do not provide a native “geographic restriction setting” for sign-up (D), app client ID validation does not stop fraudulent sign-ups (C), and using a social IdP does not provide custom accept/deny validation for all sign-ups (E).

In a properly segmented VPC architecture,public subnets route internet-bound traffic to an internet gateway, whileprivate subnets route outbound internet traffic through a NAT gatewaythat resides in a public subnet. According to the AWS Certified Security – Specialty Official Study Guide and Amazon VPC documentation, private subnets must never have a direct route to an internet gateway.

The issue described indicates that private subnets are incorrectly routing traffic directly to the internet gateway. To remediate this, aNAT gateway must be provisioned in each public subnetto ensure high availability across Availability Zones. This satisfies the requirement that private resources can initiate outbound connections without being directly reachable from the internet.

Next, the route tables associated with theprivate subnets must be updatedso that the default route (0.0.0.0/0) points to the NAT gateway in the same Availability Zone. This ensures proper traffic flow and prevents cross-AZ dependencies.

Option B is incorrect because NAT gateways must reside in public subnets. Option C is unnecessary because local routes to the VPC CIDR range are automatically created. Option E is explicitly insecure, as it would reintroduce direct internet gateway access from private subnets.

AWS documentation consistently identifiesNAT gateways plus correct private subnet routingas the standard design for secure VPC segmentation.

AWS Certified Security – Specialty Official Study Guide

Amazon VPC Route Table Documentation

AWS Well-Architected Framework – Security Pillar

Option C is the best fit because Amazon GuardDuty provides managed threat detection forEKSby analyzingEKS control plane audit logs(EKS Protection) and correlating those signals withruntime telemetry(Runtime Monitoring) that includesprocess/OS activity, network connections, and file activityon the worker nodes. This directly matches the requirement to monitor EKS audit logsin addition tooperating system, networking, and file events to detect Kubernetes security risks.

GuardDuty produces securityfindingsfor suspicious Kubernetes behavior and runtime indicators (for example, unexpected API calls, anomalous container activity, or known malicious behaviors). To notify the security team, anAmazon EventBridgerule can match GuardDuty findings and forward them to anSNS topic. SNS supportsemail subscriptions, so the team’s mailing list can receive near-real-time alerts without building a custom log parsing pipeline.

Option A (Security Hub) aggregates findings and maps to controls/standards but does not itself provide the combined audit-log + runtime event detection described. Option B combines unrelated services and still requires custom processing. Option D only alarms on “new audit logs generated,” which does not detect “security risks” and does not include OS/network/file threat detections.

AWS Elastic Disaster Recovery (AWS DRS)is purpose-built for continuously replicatingphysical and virtual serversinto AWS with low RTO/RPO. It uses lightweight replication agents to stream block-level changes to a low-coststaging areain AWS, which helps optimize storage costs (only the staging resources run continuously) and reduces bandwidth usage through efficient replication mechanisms. In a disaster or test, AWS DRS can automatically launch recovery instances in AWS based on a defined blueprint (instance types, networking, security groups), enabling rapid failover workflows that commonly meetsub-hour RTOobjectives.

Option A is not the intended service model: AWS Backup protects AWS-native resources and does not “directly replicate” arbitrary on-prem servers as a continuous replication DR system. Option B (Storage Gateway Volume Gateway) can support backups of certain storage use cases via snapshots, but it is not a general continuous replication solution for diverse physical/virtual servers and may not meet the RTO requirement as directly as AWS DRS. Option D (Direct Connect + custom automation) can help with connectivity, but it does not provide continuous server replication by itself and would require significant custom engineering and ongoing operational effort.

Therefore, enabling AWS Elastic Disaster Recovery and configuring replication agents is the best automated, cost-optimized solution.

When AWS IAM Identity Center is used to manage user access across an AWS Organization, Identity Center is the authoritative control plane for enabling and disabling user access. According to the AWS Certified Security – Specialty Official Study Guide, disabling a user in IAM Identity Center immediately prevents that user from accessing any AWS account or role that is assigned through permission sets, satisfying the requirement to stop access organization-wide.

Disabling an IAM user in a single account or removing attached policies (Options A and B) does not prevent access through IAM Identity Center–managed roles in other accounts. Option C is incomplete because removing permission sets does not immediately disable authentication and still requires querying logs from an unsupported source.

For investigation and evidence collection, AWS CloudTrail organizational event data stores provide centralized, queryable access to all management and data events across all accounts in the organization. CloudTrail Lake enables security engineers to run SQL-based queries directly against event data without exporting logs to other services. This allows rapid collection of all actions that the compromised user performed during the last 7 days.

AWS documentation explicitly identifies the combination of IAM Identity Center for access revocation and CloudTrail Lake for organization-wide investigation as a best practice for identity-related incident response.

AWS Certified Security – Specialty Official Study Guide

AWS IAM Identity Center Documentation

AWS CloudTrail Lake User Guide

AWS Incident Response Best Practices

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

Amazon Inspector is the AWS vulnerability management service that scans Lambda functions for package dependency vulnerabilities and, when enabled, Lambda code vulnerabilities. In a multi-account organization, a delegated Amazon Inspector administrator can centrally manage scan coverage and view finding results from member accounts. The Amazon Inspector dashboard provides aggregated visibility into scanned resources and findings. To keep test and development Lambda functions from appearing on the dashboard, suppression rules can hide findings that match criteria such as tags. GuardDuty Lambda Protection is for threat detection on Lambda activity, not software vulnerability scanning. AWS Shield Advanced is for DDoS protection, not Lambda vulnerability management. Therefore, Inspector delegated administration plus tag-based suppression is the correct combination.

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

An S3 gateway endpoint works through route tables. When the gateway endpoint is associated with a subnet route table, AWS automatically adds a route for the S3 prefix list that targets the gateway endpoint. Traffic from resources in that subnet to S3 then uses the private endpoint route instead of the default route through the NAT gateway. Removing the NAT route would disrupt other internet-bound workloads in the subnet and is unnecessary. Gateway endpoint policies control authorization, not route selection. Lambda security group rules do not force S3 traffic to use the gateway endpoint. The missing configuration is associating the S3 gateway endpoint with the route table used by the Lambda function’s subnet.

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When an internet-facing ALB is used as a CloudFront origin, it remains directly accessible unless additional access controls are enforced. According to AWS Certified Security – Specialty guidance,CloudFront IP allow lists alone are insufficient, because CloudFront IP ranges change and are not guaranteed to be exclusive.

The recommended and most secure approach is to configure CloudFront to send acustom origin header(such as X-Shared-Secret) with a secret value on every request to the origin. The ALB listener rules are then configured toforward traffic only when the header exists and matches the expected value. Requests that attempt to bypass CloudFront will not include this header and will be denied.

Option A is invalid because CloudFront does not support PrivateLink origins. Option B introduces unnecessary architectural changes and is not required. Option C is brittle and operationally risky due to changing IP ranges.

AWS documentation explicitly recommendscustom origin headersas the best practice to ensure that only CloudFront can access an internet-facing ALB when AWS WAF is attached at the CloudFront layer.

AWS Certified Security – Specialty Official Study Guide

Amazon CloudFront Origin Security Documentation

AWS WAF and ALB Integration Guidance

In IAM Identity Center, users see accounts and permission sets in the AWS access portal based onassignments. Here, the new permission set was assigned to theDevOps groupfor a specific member account. Sinceall developers except onecan see the permission set, the permission set itself and the account assignment are working correctly. The most likely cause is that the remaining developer isnot actually a memberof the DevOps group in the identity source (AWS Directory Service / Active Directory), or their group membership is not reflected due to missing/incorrect directory group assignment.

The least disruptive fix is to ensure the developer’s identity is correctly included in theDevOpsgroup within the directory. Once the user is a member of the assigned group (and after normal identity sync/refresh behavior), IAM Identity Center will evaluate the user as entitled to that permission set, and it will appear in the access portal.

Option B is unnecessary because the assignment is already effective for others. Option C is unrelated; service-linked roles for Organizations do not determine portal entitlements. Option D would not explain why only one user cannot see the permission set; if console access were misconfigured, it would affect all users assigned that permission set.