- A
Create an application filter that matches sftp.
Why wrong: Application filters are used for grouping, not for blocking/allowing traffic.
- B
Use QoS to limit BitTorrent traffic.
Why wrong: QoS limits bandwidth but does not block the application.
- C
Use an application override to classify all port 22 traffic as sftp.
Why wrong: This would misclassify BitTorrent traffic as sftp, bypassing the block.
- D
Create a security rule that denies application 'bittorrent' and allows application 'sftp'.
Correct: This uses App-ID to differentiate and apply appropriate actions per application.
Question 374 of 516
Use App-ID to Block BitTorrent and Allow SFTP on the Same Port
This PCNSE practice question tests your understanding of securing traffic and app-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.
An engineer wants to block the use of file-sharing application BitTorrent, but allow file transfers over SFTP which also uses port 22. What is the most effective way to achieve this using App-ID?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create a security rule that denies application 'bittorrent' and allows application 'sftp'.
D is correct because App-ID identifies applications by their unique signatures, not just ports. By creating a security rule that denies 'bittorrent' and allows 'sftp', the firewall can block BitTorrent traffic even if it uses non-standard ports, while permitting SFTP on port 22 based on its distinct application signature.
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.
- ✗
Create an application filter that matches sftp.
Why it's wrong here
Application filters are used for grouping, not for blocking/allowing traffic.
- ✗
Use QoS to limit BitTorrent traffic.
Why it's wrong here
QoS limits bandwidth but does not block the application.
- ✗
Use an application override to classify all port 22 traffic as sftp.
Why it's wrong here
This would misclassify BitTorrent traffic as sftp, bypassing the block.
- ✓
Create a security rule that denies application 'bittorrent' and allows application 'sftp'.
Why this is correct
Correct: This uses App-ID to differentiate and apply appropriate actions per application.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume port-based rules are sufficient, but App-ID is designed to identify applications by their unique signatures, not ports, so a port-based approach (like an application override) would fail to block BitTorrent if it uses the same port as SFTP.
Detailed technical explanation
How to think about this question
App-ID uses multiple identification methods including protocol decoders, application signatures, and behavioral analysis to identify applications regardless of port. For example, SFTP uses the SSH protocol on port 22, but its application signature differs from BitTorrent's DHT or peer-wire protocols. In a real-world scenario, BitTorrent can be configured to use port 22 to evade simple port-based rules, making App-ID's signature-based detection essential for accurate enforcement.
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.
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Securing Traffic and App-ID — study guide chapter
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FAQ
Questions learners often ask
What does this PCNSE question test?
Securing Traffic and App-ID — This question tests Securing Traffic and App-ID — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Create a security rule that denies application 'bittorrent' and allows application 'sftp'. — D is correct because App-ID identifies applications by their unique signatures, not just ports. By creating a security rule that denies 'bittorrent' and allows 'sftp', the firewall can block BitTorrent traffic even if it uses non-standard ports, while permitting SFTP on port 22 based on its distinct application signature.
What should I do if I get this PCNSE 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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Last reviewed: Jul 4, 2026
This PCNSE 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 PCNSE exam.
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