AWS Certified Security – Specialty (SCS-C02) — Question 209

A security engineer for a large company is managing a data processing application used by 1,500 subsidiary companies. The parent and subsidiary companies all use AWS. The application uses TCP port 443 and runs on Amazon C2 behind a Network Load Balancer (NLB). For compliance reasons, the application should only be accessible to the subsidiaries and should not be available on the public internet. To meet the compliance requirements for restricted access, the engineer has received the public and private CIDR block ranges for each subsidiary.

What solution should the engineer use to implement the appropriate access restrictions for the application?

Answer options

• A. Create a NACL to allow access on TCP port 443 from the 1,500 subsidiary CIDR block ranges. Associate the NACL to both the NLB and EC2 instances.
• B. Create an AWS security group to allow access on TCP port 443 from the 1,500 subsidiary CIDR block ranges. Associate the security group to the NLCreate a second security group for EC2 instances with access on TCP port 443 from the NLB security group.
• C. Create an AWS PrivateLink endpoint service in the parent company account attached to the NLB. Create an AWS security group for the instances to allow access on TCP port 443 from the AWS PrivateLink endpoint. Use AWS PrivateLink interface endpoints in the 1,500 subsidiary AWS accounts to connect to the data processing application.
• D. Create an AWS security group to allow access on TCP port 443 from the 1,500 subsidiary CIDR block ranges. Associate the security group with EC2 instances.

Correct answer: C

Explanation

The correct answer is C because it utilizes AWS PrivateLink to securely connect the subsidiaries to the application without exposing it to the public internet, meeting compliance needs. Option A suggests using a NACL, which is less flexible and can’t directly facilitate private connections like PrivateLink. Option B's method is incomplete as it does not fully isolate access to the application and relies on security groups alone. Option D also does not provide the necessary private connectivity solution.