SCS-C02 Threat Detection and Incident Response Practice Question
This SCS-C02 practice question tests your understanding of threat detection and incident response. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 security engineer notices that an EC2 instance is sending outbound traffic to a known malicious IP address. The engineer needs to quickly block all traffic to that IP while preserving the instance for forensic analysis. Which approach is the most effective?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Modify the instance's security group to deny outbound traffic to the malicious IP.
Modifying the security group to deny outbound traffic to that IP is quick and reversible. Using NACLs is slower and affects subnets. Stopping the instance loses volatile data. Route table modification is not effective for a single IP.
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.
✗
Stop the instance immediately.
Why it's wrong here
Stopping the instance may destroy evidence in memory.
✓
Modify the instance's security group to deny outbound traffic to the malicious IP.
Why this is correct
Security group rules can be updated quickly to block specific traffic.
Add a network ACL rule to deny outbound traffic from the instance's subnet to the malicious IP.
Why it's wrong here
NACLs are stateless and affect all instances in the subnet, not just this one.
✗
Modify the route table to route traffic to the malicious IP to a blackhole.
Why it's wrong here
Route tables are for network paths, not for blocking specific IPs.
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 healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
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 SCS-C02 subnetting questions on CIDR, address ranges, and subnet selection.
Threat Detection and Incident Response — This question tests Threat Detection and Incident Response — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Modify the instance's security group to deny outbound traffic to the malicious IP. — Modifying the security group to deny outbound traffic to that IP is quick and reversible. Using NACLs is slower and affects subnets. Stopping the instance loses volatile data. Route table modification is not effective for a single IP.
What should I do if I get this SCS-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 SCS-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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Question Discussion
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