ANS-C01 Network Security, Compliance and Governance Practice Question
This ANS-C01 practice question tests your understanding of network security, compliance and governance. 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 uses AWS WAF to protect a web application behind an Application Load Balancer. The security team notices that a specific IP address is generating a high number of requests and wants to block it immediately. What is the MOST efficient way to block this IP address?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "immediately / without restart"
Why it matters: Time or reboot constraint — the correct answer must take effect right away without requiring a reboot or reload.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Add the IP address to an IP set in AWS WAF and update the rule to block it
Option C is correct because AWS WAF allows creating an IP set and updating a rule to block it, providing immediate effect. Option A is wrong because a Network ACL can block IPs at the subnet level but requires updating the NACL, which is less granular and slower. Option B is wrong because security groups cannot block specific IPs in inbound rules for ALB traffic; they work at the instance level. Option D is wrong because creating a new web ACL and associating it takes more steps than updating an existing rule.
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.
✓
Add the IP address to an IP set in AWS WAF and update the rule to block it
Why this is correct
This is the most efficient and targeted method.
Clue confirmation
The clue word "immediately / without restart" in the question point toward this answer.
Add a deny rule in the security group attached to the ALB
Why it's wrong here
Security groups do not support deny rules; they only allow traffic.
✗
Update the Network ACL associated with the ALB subnets to deny inbound traffic from the IP address
Why it's wrong here
Network ACLs are stateless and require separate inbound/outbound rules; updating them is less efficient.
✗
Create a new web ACL in AWS WAF and associate it with the ALB
Why it's wrong here
Creating a new web ACL is more overhead than updating an existing one.
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.
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 ANS-C01 subnetting questions on CIDR, address ranges, and subnet selection.
Network Security, Compliance and Governance — This question tests Network Security, Compliance and Governance — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Add the IP address to an IP set in AWS WAF and update the rule to block it — Option C is correct because AWS WAF allows creating an IP set and updating a rule to block it, providing immediate effect. Option A is wrong because a Network ACL can block IPs at the subnet level but requires updating the NACL, which is less granular and slower. Option B is wrong because security groups cannot block specific IPs in inbound rules for ALB traffic; they work at the instance level. Option D is wrong because creating a new web ACL and associating it takes more steps than updating an existing rule.
What should I do if I get this ANS-C01 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 ANS-C01 subnetting questions on CIDR, address ranges, and subnet selection.
Are there clue words in this question I should notice?
Yes — watch for: "immediately / without restart". Time or reboot constraint — the correct answer must take effect right away without requiring a reboot or reload.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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