The answer is micro-segmentation of network resources, continuous authentication, and least privilege. These three components are critical because zero trust architecture components enforce the principle that no entity—inside or outside the network—is inherently trusted; micro-segmentation divides the network into isolated zones to contain lateral movement, continuous authentication verifies identity and device health at every access request, and least privilege restricts permissions to only what is necessary for a task. On the CompTIA SecurityX CAS-004 exam, this question tests your ability to distinguish core zero-trust mechanisms from supporting technologies like VPNs or firewalls, which are often used as distractors. A common trap is assuming that a single strong perimeter defense, such as a next-gen firewall, satisfies zero trust—but the exam emphasizes that trust must be continuously verified, not assumed based on location. Remember the mnemonic “MCL” for Micro-segmentation, Continuous authentication, and Least privilege to recall the triad that eliminates implicit trust.
CAS-004 Security Engineering Practice Question
This CAS-004 practice question tests your understanding of security engineering. 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 is implementing a zero-trust network architecture. Which THREE of the following are critical components of this approach?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Default-deny access policies (least privilege)
Zero-trust requires that no entity is trusted by default, even inside the network. Micro-segmentation, continuous authentication, and least privilege are core principles.
Key principle: Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
VPN for all remote access
Why it's wrong here
VPNs provide network-level trust, which contradicts zero-trust; instead, application-level access is preferred.
✓
Default-deny access policies (least privilege)
Why this is correct
Users and devices are given only the access necessary.
Related concept
Authentication checks who the user is.
✓
Continuous monitoring and authentication
Why this is correct
All access requests are verified regardless of location.
Related concept
Authentication checks who the user is.
✓
Micro-segmentation of network resources
Why this is correct
Isolates resources to limit lateral movement.
Related concept
Authentication checks who the user is.
✗
A single perimeter firewall
Why it's wrong here
Zero-trust eliminates the concept of a trusted internal network; a single perimeter firewall is insufficient.
Common exam traps
Common exam trap: authentication is not authorization
Logging in proves the user can authenticate. It does not automatically mean the user is allowed to enter privileged or configuration mode. Watch for AAA authorization, privilege level and command authorization details.
Detailed technical explanation
How to think about this question
This kind of question is testing the difference between identity and permission. A user may successfully log in to a router because authentication is working, but still fail to enter configuration mode because authorization is missing, misconfigured or mapped to a lower privilege level.
KKey Concepts to Remember
Authentication checks who the user is.
Authorization controls what the user is allowed to do after login.
Privilege levels affect access to EXEC and configuration commands.
AAA, TACACS+ and RADIUS can separate login success from command access.
TExam Day Tips
→Do not assume successful login means full administrative access.
→Look for words such as cannot enter configuration mode, privilege level, authorization or command access.
→Separate login problems from permission problems before choosing the answer.
Key takeaway
Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.
Real-world example
How this comes up in practice
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
Got this wrong? Here's your next step.
Review Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related CAS-004 questions on access control and AAA configuration.
Security Engineering — This question tests Security Engineering — Authentication checks who the user is..
What is the correct answer to this question?
The correct answer is: Default-deny access policies (least privilege) — Zero-trust requires that no entity is trusted by default, even inside the network. Micro-segmentation, continuous authentication, and least privilege are core principles.
What should I do if I get this CAS-004 question wrong?
Review Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related CAS-004 questions on access control and AAA configuration.
What is the key concept behind this question?
Authentication checks who the user is.
About these practice questions
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company is migrating to a zero trust architecture. Which of the following is a key principle of zero trust?
hard
A.Allow all traffic within the corporate network
✓ B.Assume breach and verify every request
C.Trust devices based on their IP address
D.Trust but verify for all internal traffic
Why B: Zero trust architecture is built on the principle of 'never trust, always verify,' which explicitly requires that every access request—regardless of origin—be authenticated, authorized, and continuously validated. Option B ('Assume breach and verify every request') captures this core tenet, as it mandates that no implicit trust is granted based on network location or device status, and every request must be treated as potentially malicious until proven otherwise.
Variation 2. Which THREE of the following are key components of a zero-trust security architecture? (Select THREE).
hard
A.VPN concentrator
✓ B.Micro-segmentation
C.Implicit trust for internal network traffic
✓ D.Least privilege access control
✓ E.Continuous monitoring of user and device behavior
Why B: Zero trust requires micro-segmentation to limit lateral movement, continuous monitoring to verify every session, and least privilege access to enforce minimal permissions. VPN is a perimeter technology, and implicit trust violates zero trust principles.
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Question Discussion
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