AWS Certified Solutions Architect – Professional (SAP-C02) — Question 158

A company has a website that runs on Amazon EC2 instances behind an Application Load Balancer (ALB). The instances are in an Auto Scaling group. The ALB is associated with an AWS WAF web ACL.

The website often encounters attacks in the application layer. The attacks produce sudden and significant increases in traffic on the application server. The access logs show that each attack originates from different IP addresses. A solutions architect needs to implement a solution to mitigate these attacks.

Which solution will meet these requirements with the LEAST operational overhead?

Answer options

• A. Create an Amazon CloudWatch alarm that monitors server access. Set a threshold based on access by IP address. Configure an alarm action that adds the IP address to the web ACL’s deny list.
• B. Deploy AWS Shield Advanced in addition to AWS WAF. Add the ALB as a protected resource.
• C. Create an Amazon CloudWatch alarm that monitors user IP addresses. Set a threshold based on access by IP address. Configure the alarm to invoke an AWS Lambda function to add a deny rule in the application server’s subnet route table for any IP addresses that activate the alarm.
• D. Inspect access logs to find a pattern of IP addresses that launched the attacks. Use an Amazon Route 53 geolocation routing policy to deny traffic from the countries that host those IP addresses.

Correct answer: B

Explanation

The correct answer is B because AWS Shield Advanced provides additional protection against DDoS attacks and integrates seamlessly with AWS WAF, thus minimizing operational overhead. Option A requires manual updates to the deny list, which can be labor-intensive. Option C involves invoking a Lambda function, adding complexity and operational overhead. Option D relies on manual analysis of logs and geolocation policies, which is not as effective or efficient as using a dedicated service like AWS Shield.