AWS Certified Security – Specialty (SCS-C02) — Question 185

A company deployed an Amazon EC2 instance to a VPC on AWS. A recent alert indicates that the EC2 instance is receiving a suspicious number of requests over an open TCP port from an external source. The TCP port remains open for long periods of time.

The company's security team needs to stop all activity to this port from the external source to ensure that the EC2 instance is not being compromised. The application must remain available to other users.

Which solution will meet these requirements?

Answer options

• A. Update the network ACL that is attached to the subnet that is associated with the EC2 instance. Add a Deny statement for the port and the source IP addresses.
• B. Update the elastic network interface security group that is attached to the EC2 instance to remove the port from the inbound rule list.
• C. Update the elastic network interface security group that is attached to the EC2 instance by adding a Deny entry in the inbound list for the port and the source IP addresses.
• D. Create a new network ACL for the subnet. Deny all traffic from the EC2 instance to prevent data from being removed.

Correct answer: A

Explanation

The correct answer is A because updating the network ACL allows for a specific Deny statement to be applied to the port and source IPs without affecting other users. Option B would remove access to the port entirely, which could affect legitimate users, while C is incorrect as security groups do not support Deny rules. Option D incorrectly suggests blocking all traffic from the EC2 instance, which would disrupt the application for all users.