The correct answers are to allow only necessary ports and protocols and to implement stateful inspection, as these two principles directly enforce least privilege and intelligent traffic filtering in firewall policy design. Allowing only necessary ports and protocols ensures that only explicitly required services are permitted, reducing the attack surface, while stateful inspection tracks the state of active connections to make dynamic, context-aware decisions about which packets to allow. On the CompTIA SecurityX CAS-004 exam, this question tests your ability to distinguish core design principles from operational tasks or insecure defaults—a common trap is choosing “default allow” or “logging,” which are either fundamentally insecure or not design principles. Remember the mnemonic “LIPS”: Least privilege via ports, Inspection via stateful, Policy design, Security first.
CAS-004 Security Architecture Practice Question
This CAS-004 practice question tests your understanding of security architecture. 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 architect is reviewing firewall rules for a new application tier. Which TWO of the following principles should be applied when designing the firewall policy? (Choose two.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Implement stateful packet inspection
Allowing only necessary ports and protocols (B) implements least privilege, and implementing stateful packet inspection (C) enables intelligent traffic filtering. Default allow (A) is insecure, static IPs (D) are not a principle, and logging (E) is operational, not a design principle.
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.
✗
Log all denied traffic
Why it's wrong here
Logging is important for monitoring but is not a design principle for rule structure.
✗
Use static IP addresses for all servers
Why it's wrong here
Static IPs are a network configuration, not a firewall design principle.
✓
Implement stateful packet inspection
Why this is correct
Stateful inspection allows rules based on connection state, improving security.
Related concept
Authentication checks who the user is.
✗
Default allow all traffic
Why it's wrong here
Default allow violates least privilege and is insecure.
✓
Allow only necessary ports and protocols
Why this is correct
This implements the principle of least privilege.
Related concept
Authentication checks who the user is.
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 junior network technician can log in to a core router but cannot reach the enable prompt or configuration mode. The AAA server is authenticating the login — but the authorisation policy only grants privilege level 1, not 15. Authentication (who you are) is working; authorisation (what you can do) is not.
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 Architecture — This question tests Security Architecture — Authentication checks who the user is..
What is the correct answer to this question?
The correct answer is: Implement stateful packet inspection — Allowing only necessary ports and protocols (B) implements least privilege, and implementing stateful packet inspection (C) enables intelligent traffic filtering. Default allow (A) is insecure, static IPs (D) are not a principle, and logging (E) is operational, not a design principle.
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.
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