AWS Certified Security – Specialty — Question 199

A company is implementing a new application in a new AWS account. A VPC and subnets have been created for the application. The application has been peered to an existing VPC in another account in the same AWS Region for database access. Amazon EC2 instances will regularly be created and terminated in the application VPC, but only some of them will need access to the databases in the peered VPC over TCP port 1521. A security engineer must ensure that only the
EC2 instances than need access to the databases can access them through the network.
How can the security engineer implement this solution?

Answer options

• A. Create a new security group in the database VPC and create an inbound rule that allows all traffic from the IP address range of the application VPC. Add a new network ACL rule on the database subnets. Configure the rule to TCP port 1521 from the IP address range of the application VPC. Attach the new security group to the database instances that the application instances need to access.
• B. Create a new security group in the application VPC with an inbound rule that allows the IP address range of the database VPC over TCP port 1521. Create a new security group in the database VPC with an inbound rule that allows the IP address range of the application VPC over port 1521. Attach the new security group to the database instances and the application instances that need database access.
• C. Create a new security group in the application VPC with no inbound rules. Create a new security group in the database VPC with an inbound rule that allows TCP port 1521 from the new application security group in the application VPC. Attach the application security group to the application instances that need database access, and attach the database security group to the database instances.
• D. Create a new security group in the application VPC with an inbound rule that allows the IP address range of the database VPC over TCP port 1521. Add a new network ACL rule on the database subnets. Configure the rule to allow all traffic from the IP address range of the application VPC. Attach the new security group to the application instances that need database access.

Correct answer: C

Explanation

The correct answer is C because it allows only the EC2 instances that need database access to connect by linking the application security group to the database security group. Option A and D are incorrect as they allow broader access through network ACLs, which is not necessary. Option B is also wrong because it permits access from the application VPC to the database VPC indiscriminately, rather than restricting access to specific instances.