The correct answer is to create a flow log and use a subscription filter in CloudWatch Logs to include only records with 'ACCEPT'. This works because every VPC Flow Log record contains an action field that explicitly marks each entry as either ACCEPT or REJECT, allowing you to filter on that status directly. On the AWS Certified Security Specialty SCS-C02 exam, this question tests your understanding that flow logs capture all traffic metadata, but the filtering must happen at the CloudWatch Logs subscription level, not by modifying security groups or network ACLs, which control access but do not filter logged records. A common trap is assuming that security group rules inherently log only accepted traffic—they do not; flow logs log both accepted and rejected traffic based on the actual packet verdict. Remember the key distinction: security groups and NACLs enforce rules, but flow logs record the result, so you must filter the log output itself. Memory tip: think of the flow log as a camera that records everything, and the subscription filter as the editor that keeps only the "ACCEPT" scenes.
SCS-C02 Security Logging and Monitoring Practice Question
This SCS-C02 practice question tests your understanding of security logging and monitoring. 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 DevOps engineer is configuring VPC Flow Logs for a subnet that contains a public-facing Application Load Balancer (ALB). The engineer wants to capture only accepted traffic for security analysis. What should the engineer do?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create a flow log and use a subscription filter in CloudWatch Logs to include only records with 'ACCEPT'.
VPC Flow Logs can filter by acceptance status. The 'accept' field in the flow log record indicates whether traffic was accepted or rejected. Setting a filter to capture only 'ACCEPT' records meets the requirement. Option A is wrong because security groups accept all traffic allowed by rules. Option C is wrong because network ACLs also accept traffic. Option D is wrong because changing the format does not filter.
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.
✓
Create a flow log and use a subscription filter in CloudWatch Logs to include only records with 'ACCEPT'.
Why this is correct
CloudWatch Logs subscription filter can be used to filter flow log records based on the 'action' field.
Configure the security group to log only accepted traffic.
Why it's wrong here
Security groups do not log traffic; they only allow or deny.
✗
Use the default flow log format and filter at the S3 bucket using S3 Select.
Why it's wrong here
S3 Select is for querying, not real-time filtering of flow logs.
✗
Create a flow log with a custom format that includes the 'action' field, and filter for 'ACCEPT'.
Why it's wrong here
Custom format does not filter; you need to filter at the destination.
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 media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
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.
Security Logging and Monitoring — This question tests Security Logging and Monitoring — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Create a flow log and use a subscription filter in CloudWatch Logs to include only records with 'ACCEPT'. — VPC Flow Logs can filter by acceptance status. The 'accept' field in the flow log record indicates whether traffic was accepted or rejected. Setting a filter to capture only 'ACCEPT' records meets the requirement. Option A is wrong because security groups accept all traffic allowed by rules. Option C is wrong because network ACLs also accept traffic. Option D is wrong because changing the format does not filter.
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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