This CAS-004 practice question tests your understanding of security architecture. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 wants to protect sensitive data stored in a public cloud bucket. Which of the following is the MOST effective control to prevent accidental public exposure?
Enable bucket logging
Why wrong: Logging is detective, not preventive.
Implement lifecycle policies
Why wrong: Lifecycle policies manage data retention, not access control.
Use server-side encryption
Why wrong: Encryption protects data but does not prevent public access.
Apply resource-based policies with explicit deny for public access
Explicit deny prevents any public access, even if other permissions accidentally allow it.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Apply resource-based policies with explicit deny for public access
Applying resource-based policies with an explicit deny for public access directly prevents public exposure. Bucket logging, encryption, and lifecycle policies are important but do not prevent accidental exposure.
Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Enable bucket logging
Why it's wrong here
Logging is detective, not preventive.
Implement lifecycle policies
Why it's wrong here
Lifecycle policies manage data retention, not access control.
Use server-side encryption
Why it's wrong here
Encryption protects data but does not prevent public access.
Apply resource-based policies with explicit deny for public access
Why this is correct
Explicit deny prevents any public access, even if other permissions accidentally allow it.
Related concept
Standard ACLs match source addresses.
Common exam traps
ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.
Detailed technical explanation
ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.
Key takeaway
ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
Real-world example
A security administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.
What to study next
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related CAS-004 ACL questions on filtering logic and placement.
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FAQ
Security Architecture — This question tests Security Architecture — Standard ACLs match source addresses..
The correct answer is: Apply resource-based policies with explicit deny for public access — Applying resource-based policies with an explicit deny for public access directly prevents public exposure. Bucket logging, encryption, and lifecycle policies are important but do not prevent accidental exposure.
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related CAS-004 ACL questions on filtering logic and placement.
Standard ACLs match source addresses.
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Last reviewed: Jun 24, 2026
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