- A
Disable the WAF rules that are causing false positives and add network ACLs to block all traffic to the database except from the ALB.
Why wrong: Disabling WAF rules would leave the application vulnerable to SQL injection, and network ACLs alone do not provide the same level of granular access control as IAM policies for database access.
- B
Remove the WAF web ACL and rely on security group ingress rules that allow all traffic from the VPC CIDR to the database.
Why wrong: Removing the WAF web ACL exposes the application to SQL injection, and allowing all traffic from the VPC CIDR is too permissive for database security.
- C
Switch the WAF web ACL to count mode and add a second ALB in front of the database to filter traffic.
Why wrong: Adding a second ALB is unnecessary and adds complexity. Using count mode alone without an IAM policy does not address restricting database access to approved services, and the false positive issue remains.
- D
Switch the WAF web ACL to count mode while tuning the rules, and implement an IAM policy to restrict database access to specific AWS services using the aws:SourceArn condition key.
Switching to count mode allows monitoring and tuning of WAF rules to eliminate false positives while still detecting SQL injection. Implementing an IAM policy with the aws:SourceArn condition key restricts database access to only approved AWS services, enhancing security beyond network controls.
DOP-C02 Security and Compliance Practice Question
This DOP-C02 practice question tests your understanding of security and compliance. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company runs a web application on Amazon ECS with Fargate launch type behind an Application Load Balancer (ALB). The application uses an RDS MySQL database. The security team performed a penetration test and discovered that the application is vulnerable to SQL injection. The development team has deployed a WAF web ACL to the ALB that includes rules to block SQL injection attacks. However, after the deployment, the application started returning 403 errors for legitimate requests, and the security team needs to investigate. The team also wants to ensure that only approved AWS services can access the RDS database. The current security groups are configured with a rule that allows inbound traffic from the ALB security group to the RDS database on port 3306. Which combination of actions should the security team take to resolve the issue and improve the security posture?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Switch the WAF web ACL to count mode while tuning the rules, and implement an IAM policy to restrict database access to specific AWS services using the aws:SourceArn condition key.
Option D is the correct answer. Switching the WAF web ACL to count mode allows the security team to monitor requests that would be blocked without actually blocking them, enabling them to fine-tune the rules to eliminate false positives while still protecting against SQL injection. Additionally, implementing an IAM policy with the aws:SourceArn condition key can restrict database access to only approved AWS services, such as Lambda functions or specific EC2 instances, enhancing the security posture beyond just network-level controls. Option A is incorrect because disabling WAF rules would leave the application vulnerable, and network ACLs are stateless and not sufficient for fine-grained access control. Option B is incorrect because relying solely on security groups with VPC CIDR allows broad access and does not address the false positive issue. Option C is incorrect because adding a second ALB is unnecessary and does not solve the false positive problem, and using count mode alone without IAM policy does not address database access restrictions.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Disable the WAF rules that are causing false positives and add network ACLs to block all traffic to the database except from the ALB.
Why it's wrong here
Disabling WAF rules would leave the application vulnerable to SQL injection, and network ACLs alone do not provide the same level of granular access control as IAM policies for database access.
- ✗
Remove the WAF web ACL and rely on security group ingress rules that allow all traffic from the VPC CIDR to the database.
- ✗
Switch the WAF web ACL to count mode and add a second ALB in front of the database to filter traffic.
Why it's wrong here
Adding a second ALB is unnecessary and adds complexity. Using count mode alone without an IAM policy does not address restricting database access to approved services, and the false positive issue remains.
- ✓
Switch the WAF web ACL to count mode while tuning the rules, and implement an IAM policy to restrict database access to specific AWS services using the aws:SourceArn condition key.
Why this is correct
Switching to count mode allows monitoring and tuning of WAF rules to eliminate false positives while still detecting SQL injection. Implementing an IAM policy with the aws:SourceArn condition key restricts database access to only approved AWS services, enhancing security beyond network controls.
Related concept
CIDR notation defines the prefix length.
Common exam traps
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
- CIDR notation defines the prefix length.
- Block size helps identify subnet boundaries.
- Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
- The required host count determines the smallest suitable subnet.
TExam Day Tips
- Write the block size before choosing the subnet.
- Check whether the question asks for hosts, subnets or a specific address range.
- Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Real-world example
How this comes up in practice
A company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
Visual reference
Quick reference
Cloud Service Model Comparison
| Model | You Manage | Provider Manages | Examples |
|---|---|---|---|
| IaaS | OS, runtime, apps, data | Hardware, hypervisor, networking | EC2, Azure VMs, GCP Compute Engine |
| PaaS | Apps and data | OS, runtime, middleware, hardware | Elastic Beanstalk, Azure App Service |
| SaaS | Data and settings only | Everything else | Microsoft 365, Salesforce, Workday |
| FaaS / Serverless | Function code only | Infra, scaling, runtime | Lambda, Azure Functions, Cloud Run |
| CaaS | Containers and apps | Kubernetes, OS, hardware | EKS, AKS, GKE |
What to study next
Got this wrong? Here's your next step.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related DOP-C02 subnetting questions on CIDR, address ranges, and subnet selection.
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Security and Compliance — study guide chapter
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FAQ
Questions learners often ask
What does this DOP-C02 question test?
Security and Compliance — This question tests Security and Compliance — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Switch the WAF web ACL to count mode while tuning the rules, and implement an IAM policy to restrict database access to specific AWS services using the aws:SourceArn condition key. — Option D is the correct answer. Switching the WAF web ACL to count mode allows the security team to monitor requests that would be blocked without actually blocking them, enabling them to fine-tune the rules to eliminate false positives while still protecting against SQL injection. Additionally, implementing an IAM policy with the aws:SourceArn condition key can restrict database access to only approved AWS services, such as Lambda functions or specific EC2 instances, enhancing the security posture beyond just network-level controls. Option A is incorrect because disabling WAF rules would leave the application vulnerable, and network ACLs are stateless and not sufficient for fine-grained access control. Option B is incorrect because relying solely on security groups with VPC CIDR allows broad access and does not address the false positive issue. Option C is incorrect because adding a second ALB is unnecessary and does not solve the false positive problem, and using count mode alone without IAM policy does not address database access restrictions.
What should I do if I get this DOP-C02 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related DOP-C02 subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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Last reviewed: Jun 20, 2026
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