This PCNSA practice question tests your understanding of app-id and content-id. 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.
Refer to the exhibit. An administrator wants to block all traffic that does not match a specific application (e.g., only allow 'web-browsing'). What should be done?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Change action to 'deny' and create a new rule with application ['web-browsing'] above it.
Option D is correct because to enforce an allow-list approach for a specific application like 'web-browsing', you must first create a rule that denies all traffic (action 'deny') and then place a higher-priority rule above it that explicitly allows only 'web-browsing'. This ensures that any traffic not matching the allowed application is blocked by the default-deny rule, leveraging App-ID's ability to identify applications regardless of port or protocol.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Use a file blocking profile.
Why it's wrong here
File blocking blocks file types, not applications.
✗
Change application to ['unknown-tcp', 'unknown-udp'].
Why it's wrong here
That would only block unidentified traffic, not all non-web-browsing apps.
✗
Change category to ['misccategory'].
Why it's wrong here
Categories are not used to block applications.
✓
Change action to 'deny' and create a new rule with application ['web-browsing'] above it.
Why this is correct
A deny-all rule at the bottom with specific allow rules above is best practice.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Palo Alto Networks often tests the misconception that you can block all non-matching traffic by simply changing the action of the existing rule to 'deny' without adding a separate allow rule above it, but that would block everything including the desired application.
Detailed technical explanation
How to think about this question
Under the hood, App-ID performs deep packet inspection (DPI) to identify applications by their unique signatures, even if they use non-standard ports. The rule order is critical: Palo Alto Networks firewalls evaluate security rules from top to bottom, and the first match determines the action. By placing the allow rule for 'web-browsing' above the deny-all rule, you ensure that only HTTP/HTTPS traffic (identified as 'web-browsing') is permitted, while all other traffic—including unknown applications, custom protocols, or misclassified traffic—is denied. This is a common zero-trust or least-privilege application control strategy.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
App-ID and Content-ID — This question tests App-ID and Content-ID — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Change action to 'deny' and create a new rule with application ['web-browsing'] above it. — Option D is correct because to enforce an allow-list approach for a specific application like 'web-browsing', you must first create a rule that denies all traffic (action 'deny') and then place a higher-priority rule above it that explicitly allows only 'web-browsing'. This ensures that any traffic not matching the allowed application is blocked by the default-deny rule, leveraging App-ID's ability to identify applications regardless of port or protocol.
What should I do if I get this PCNSA question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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