AWS Certified Security – Specialty — Question 71

An organization operates a web application that serves users globally. The application runs on Amazon EC2 instances behind an Application Load Balancer.
There is an Amazon CloudFront distribution in front of the load balancer, and the organization uses AWS WAF. The application is currently experiencing a volumetric attack whereby the attacker is exploiting a bug in a popular mobile game.
The application is being flooded with HTTP requests from all over the world with the User-Agent set to the following string: Mozilla/5.0 (compatible; ExampleCorp;
ExampleGame/1.22; Mobile/1.0)
What mitigation can be applied to block attacks resulting from this bug while continuing to service legitimate requests?

Answer options

• A. Create a rule in AWS WAF rules with conditions that block requests based on the presence of ExampleGame/1.22 in the User-Agent header
• B. Create a geographic restriction on the CloudFront distribution to prevent access to the application from most geographic regions
• C. Create a rate-based rule in AWS WAF to limit the total number of requests that the web application services.
• D. Create an IP-based blacklist in AWS WAF to block the IP addresses that are originating from requests that contain ExampleGame/1.22 in the User-Agent header.

Correct answer: A

Explanation

The correct answer is A because creating a rule in AWS WAF that specifically targets the User-Agent string allows direct blocking of the malicious traffic without affecting legitimate requests. Option B is ineffective as it would restrict users from legitimate geographic regions. Option C may not stop the attack entirely, as it only limits the rate of requests rather than blocking specific malicious ones. Option D could potentially block legitimate users if their IP addresses overlap with those of attackers, making it a less precise solution.