Question

Difficulty: EasyNetwork and Infrastructure Security

A cloud administrator wants to configure network security for a new application deployment in a Virtual Private Cloud (VPC). Which TWO of the following statements correctly describe the behavior and boundaries of Security Groups and Network Access Control Lists (Network ACLs)? (Select TWO.)

  1. Security Groups are stateful (automatically allowing return traffic), whereas Network ACLs are stateless (requiring explicit inbound and outbound rules).Answer
  2. Security Groups operate at the instance level, whereas Network ACLs operate at the subnet level.Answer
  3. C
    Security Groups are stateless, meaning outbound rules must be manually configured to allow return traffic.
  4. D
    Network ACLs are applied to individual EC2 instances to control host-level traffic.
  5. E
    Both Security Groups and Network ACLs are managed exclusively by AWS under the Shared Responsibility Model.

Answer

Security Groups are stateful, whereas Network ACLs are stateless; and Security Groups operate at the instance level, whereas Network ACLs operate at the subnet level.
Security Groups operate at the instance level (specifically elastic network interfaces) and are stateful, automatically allowing return traffic. Network ACLs operate at the subnet level and are stateless, requiring separate inbound and outbound rules to permit return traffic.

Step-by-Step Solution

1
Analyze the stateful vs. stateless nature of the two security services.
Security Groups are stateful, meaning they track connections and automatically allow returning traffic. Network ACLs are stateless, meaning they process inbound and outbound traffic independently.
This helps identify which rules need to be configured for traffic flow.
2
Determine where Security Groups and Network ACLs are applied in the network hierarchy.
Security Groups are applied to elastic network interfaces (instance level), while Network ACLs are associated with subnets (subnet level).
This defines the boundary of control for each security layer.

Key Concept

The operational level and connection tracking state of Security Groups and Network ACLs.
Rate this question