Question

Difficulty: MediumAWS Network Services

A company is configuring network security controls for a web application deployed on Amazon EC2 instances within a single subnet. The security team wants to apply stateless filtering at the subnet boundary to block specific malicious IP addresses, while allowing developers to manage stateful firewall rules at the individual instance level. Which TWO of the following AWS network security features should the team configure to achieve this?

  1. Network Access Control Lists (Network ACLs) to enforce stateless traffic filtering at the subnet boundaryAnswer
  2. B
    AWS Transit Gateway to route and inspect traffic between the subnet boundary and the EC2 instances
  3. Security Groups to enforce stateful traffic filtering at the EC2 instance levelAnswer
  4. D
    Security Groups configured at the subnet boundary to perform stateless IP blocking
  5. E
    Network Access Control Lists (Network ACLs) configured at the EC2 instance level to manage stateful rule tracking

Answer

Network Access Control Lists (Network ACLs) to enforce stateless traffic filtering at the subnet boundary, and Security Groups to enforce stateful traffic filtering at the EC2 instance level.
To implement stateless filtering at the subnet boundary to block malicious IPs, Network Access Control Lists (Network ACLs) must be used. To implement stateful filtering at the individual EC2 instance level, Security Groups must be used.

Step-by-Step Solution

1
Identify the subnet-level stateless filtering requirement.
Network Access Control Lists (Network ACLs) are selected.
Network ACLs operate at the subnet level and support stateless rules, allowing explicit denial of traffic from specific IP addresses.
2
Identify the instance-level stateful filtering requirement.
Security Groups are selected.
Security Groups act as stateful firewalls at the instance level, allowing developers to manage rule sets without manually tracking return traffic.

Key Concept

The difference between Security Groups (stateful, instance-level) and Network ACLs (stateless, subnet-level).
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