PCNSA Securing Traffic Practice Question
A financial services company uses a Palo Alto Networks PA-5220 firewall in an active/passive HA pair at their headquarters. They have a single zone 'Trust-LAN' for internal users and a single zone 'Untrust-WAN' for internet traffic. The security policy currently includes a rule that allows all outbound HTTP/HTTPS traffic from 'Trust-LAN' to 'Untrust-WAN' with no security profiles applied. Recently, users have been complaining about slow internet performance, and the IT team suspects malware or botnet activity. The firewall's logs show numerous sessions to known malicious IPs, but the firewall is not blocking them. The network architect decides to implement URL Filtering and Threat Prevention profiles on the outbound rule. However, after committing the changes, some users report that legitimate websites (e.g., online banking, cloud apps) are being blocked. The IT team verifies that the URL Filtering profile is set to 'alert' for all categories except 'malware' which is 'block', and the Threat Prevention profile is set to 'default' action. What is the most likely cause of the legitimate website blocking?
⚠ Common exam trap
Test-takers frequently assume only the explicitly mentioned categories (e.g., 'malware') matter, overlooking the 'uncategorized' category which is often set to 'block' by default or inadvertently, causing legitimate traffic to be blocked.
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
✓
The URL Filtering profile's 'uncategorized' category is set to 'block', blocking sites not in the URL database.
The URL Filtering profile is set to 'alert' for all categories except 'malware' which is 'block'. However, if the 'uncategorized' category is set to 'block', any website not yet categorized in Palo Alto Networks' URL database (e.g., new or less common legitimate sites like online banking portals or cloud apps) will be blocked. This explains why legitimate sites are being blocked despite the profile being permissive for known categories.
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 URL Filtering profile's 'uncategorized' category is set to 'block', blocking sites not in the URL database.
Why this is correct
This is a common cause: uncategorized URLs are blocked by default if the action is not 'alert'.
- ✗
The security rule order is incorrect; a deny rule above the allow rule is blocking legitimate traffic.
Why it's wrong here
The issue is not about rule order; the allow rule is still in place.
- ✗
The URL Filtering profile is applied at the zone level, not per rule, causing all traffic to be filtered.
Why it's wrong here
URL profiles are applied per rule, not per zone.
- ✗
The firewall has insufficient memory to process URL lookups and is dropping packets.
Why it's wrong here
Resource exhaustion is unlikely; the firewall should handle the load.
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JA
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.