This PCNSA practice question tests your understanding of app-id and content-id. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 administrator notices that traffic from a custom application is being incorrectly identified as web-browsing. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The custom application uses HTTP but no specific App-ID signature.
Option C is correct because when a custom application uses HTTP but lacks a specific App-ID signature, Palo Alto Networks firewalls default to classifying the traffic as web-browsing (HTTP). App-ID relies on a combination of protocol decoders and application signatures; without a custom App-ID signature defined for the application, the firewall cannot distinguish it from generic HTTP traffic.
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.
✗
The application signature database is outdated.
Why it's wrong here
An outdated database would cause incorrect identification for many applications, not just custom ones.
✗
App-ID is disabled on the security rule.
Why it's wrong here
If App-ID were disabled, traffic would appear as 'unknown-tcp' or 'unknown-udp'.
✓
The custom application uses HTTP but no specific App-ID signature.
Why this is correct
Without a custom signature, App-ID may classify the traffic as web-browsing.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Content-ID is blocking the application.
Why it's wrong here
Content-ID does not affect application identification; it enforces security policies.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Palo Alto Networks often tests the misconception that an outdated signature database is the root cause, but the trap here is that the custom application has no signature at all, so updating the database would not help—the administrator must create a custom App-ID signature or use an application override.
Detailed technical explanation
How to think about this question
Under the hood, App-ID uses protocol decoders (e.g., HTTP decoder) to parse traffic and then applies application signatures. If no signature matches, the firewall falls back to the protocol decoder's default classification, which for HTTP is 'web-browsing'. To correctly identify a custom application, an administrator must create a custom App-ID signature using the application override feature or define a custom application with specific attributes (e.g., custom TCP port, SSL decryption, or payload patterns). In real-world scenarios, this often occurs with proprietary enterprise applications that tunnel over HTTP but are not recognized by the default signature set.
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 small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
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: The custom application uses HTTP but no specific App-ID signature. — Option C is correct because when a custom application uses HTTP but lacks a specific App-ID signature, Palo Alto Networks firewalls default to classifying the traffic as web-browsing (HTTP). App-ID relies on a combination of protocol decoders and application signatures; without a custom App-ID signature defined for the application, the firewall cannot distinguish it from generic HTTP traffic.
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.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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This PCNSA practice question is part of Courseiva's free Palo Alto Networks certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the PCNSA exam.
Question Discussion
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