PCNSA App-ID and Content-ID Practice Question
An administrator wants to block all peer-to-peer file sharing traffic, but must ensure that legitimate business applications like FTP are not affected. Which approach is most effective?
⚠ Common exam trap
Many exam-takers assume port-based blocking (Options B and C) is sufficient, but App-ID is designed to decouple application identity from port, making port-based rules ineffective against modern P2P traffic that uses port evasion techniques.
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 an Application Filter that matches all P2P applications and use it in a deny rule.
Palo Alto Networks App-ID can identify peer-to-peer (P2P) traffic by application signature, regardless of port. Creating an Application Filter that matches all P2P applications (e.g., BitTorrent, eDonkey, Gnutella) and applying it in a deny rule ensures all P2P traffic is blocked while legitimate business applications like FTP (which uses distinct App-ID signatures) are not affected, as App-ID decodes traffic at Layer 7.
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 all P2P applications and use it in a deny rule.
Why this is correct
An Application Filter groups all peer-to-peer applications by App-ID, and referencing it in a deny rule blocks that traffic while FTP, identified as a distinct application, remains permitted. This satisfies both the blocking and the legitimate-traffic constraints.
- ✗
Create a security rule with 'application none' and block the common P2P ports.
Why it's wrong here
Blocking common P2P ports fails because modern P2P clients hop ports, use HTTP/HTTPS, or tunnel, while port-based rules also catch legitimate FTP and other services sharing those ports. It is tempting because port blocking is simple and familiar, and would be correct for legacy protocols that always use fixed, dedicated ports.
- ✗
Use a Service object to block all ports typically used by P2P applications.
Why it's wrong here
Service objects match TCP/UDP ports, not applications, so P2P traffic on non-standard or dynamic ports bypasses the rule while FTP on port 21 may be caught if listed. It is tempting because service objects are reusable and easy to build, and would be correct for blocking a known service on a fixed port.
- ✗
Identify each known P2P application and add them individually to a block rule.
Why it's wrong here
Enumerating individual P2P applications is incomplete — new or renamed variants escape the rule, and the list requires constant maintenance. It is tempting because explicit allow/deny lists feel precise, and would be correct in a tightly controlled environment where only a fixed, known set of applications is permitted.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.