A. The firewall denied the traffic before the application match could be performed.

Explanation:
The key to understanding this lies in the Palo Alto Networks firewall's policy evaluation order, specifically the relationship between rules that block traffic and the App-ID process.

App-ID is a powerful feature, but it does not happen first. The firewall processes traffic in a specific sequence. If a security rule with a Deny action matches the traffic based on earlier criteria (like Source/Destination Zone, Address, or User), the session is immediately dropped. The firewall does not invest resources in performing deep packet inspection (App-ID) on traffic it has already decided to block.

When this happens, the Traffic log will show the Application as not-applicable because the application was never identified.

Why the other options are incorrect:
B. The TCP connection terminated without identifying any application data and C.
There was not enough application data after the TCP connection was established: These scenarios are related to the App-ID process itself. In these cases, the firewall attempted to identify the application but could not. This would typically result in the application being labeled as incomplete or falling back to a base protocol (like ssl or tcp), not not-applicable.

D. The application is not a known Palo Alto Networks App-ID:
If the firewall processes the traffic (allows it through a rule) and successfully identifies it as an unknown application, it will be classified under the unknown application or, more commonly, unknown-tcp or unknown-udp. Again, this is different from not-applicable.

🔍 Reference:

Palo Alto Networks – Traffic Log Fields
Palo Alto Knowledge Base – Why Application is 'not-applicable'

C. It tries to establish a tunnel to the GlobalProtect gateway using SSL/TLS.

Explanation:
By default, when the GlobalProtect app fails to establish an IPSec tunnel to the GlobalProtect gateway, it automatically falls back to SSL/TLS to maintain connectivity. This fallback mechanism ensures that users can still connect securely even if IPSec is blocked by network restrictions (e.g., NAT traversal issues, firewall rules, or unsupported ports).
This behavior is part of GlobalProtect’s resilient tunnel negotiation logic, designed to prioritize IPSec for performance but guarantee access via SSL/TLS if needed.
As confirmed in Palo Alto’s documentation and PCNSE prep resources:
“If the GlobalProtect app fails to establish an IPSec tunnel with the GlobalProtect gateway, the default behavior is to fallback to SSL/TLS for tunnel establishment”.

❌ Why the other options are incorrect
A. Tunnel to the portal using SSL/TLS:
The portal is used for configuration and authentication—not for tunnel establishment. VPN tunnels are always built to the gateway, not the portal.
B. Stops tunnel-establishment immediately:
Incorrect. The app does not abandon the connection—it attempts SSL/TLS fallback to maintain access.
D. Keeps trying IPSec only:
False. It does not persist with IPSec indefinitely. It switches to SSL/TLS if IPSec fails.

A. show system setting ssl-decrypt certificate

Explanation:
This is the primary CLI command used to display the details of all certificates installed on the firewall that are specifically used for SSL Decryption. This includes:

Forward Trust Certificate:
The CA certificate used to sign the dynamically generated certificates for sites in the Forward Trust list (sites that will not be decrypted).
Forward Untrust Certificate:
The CA certificate used to sign the dynamically generated certificates for sites that are decrypted using SSL Forward Proxy.
SSL Inbound Inspection Certificate:
The certificate (and its private key) presented by the firewall when it acts as the server for inbound decrypted connections.
Running this command provides a summary of these key certificates, including their issuers, expiration dates, and other details, which is essential for troubleshooting decryption failures.

Why the Other Options Are Incorrect:
B. show system setting ssl-decrypt certs:
This is not a valid CLI command.
C. debug dataplane show ssl-decrypt ssl-certs:
This is not a standard, documented command for viewing the configured decryption certificates. It appears to be a malformed attempt at a dataplane debug command, which would be used for much lower-level packet analysis, not for viewing certificate configurations.
D. show system setting ssl-decrypt certificate-cache:
This command is used to view the cache of dynamically generated certificates, not the root CA certificates used to generate them. It's for troubleshooting performance or cache-related issues, not for checking the core configuration of the Forward Trust/Untrust CAs.

Valid Reference:
Palo Alto Networks Administrator Guide | SSL Decryption | Troubleshoot SSL Decryption | CLI Commands: The official documentation lists the show system setting ssl-decrypt certificate command as the method to "display the forward trust certificate, forward untrust certificate, and the certificates used for inbound inspection." This is the definitive command for this purpose.

A. an Authentication policy with 'unknown' selected in the Source User field

Explanation:
To authenticate a user on a new BYOD (Bring Your Own Device) that isn't part of the corporate domain, a network security administrator needs to configure an Authentication policy. This policy should be set to match traffic where the source user is 'unknown'.
1.Authentication Policy: This type of policy's primary function is to trigger user authentication. It directs the user to a captive portal or some other form of authentication method before allowing them access to network resources.
2.unknown' User:
When a user with a new device connects to the network, the Palo Alto Networks firewall initially doesn't have any identity information about them. The firewall classifies their traffic as coming from an 'unknown' user.
3.Authentication Workflow:
The user's device attempts to access a resource (e.g., a website).
The firewall's security policy allows the traffic to proceed, but the Authentication policy with the 'unknown' source user matches the session.
This match triggers the authentication mechanism, such as a Captive Portal.
The user is redirected to the portal to enter their credentials.
Once authenticated, the firewall learns the user's identity and can apply more specific security policies to their traffic.

The other options are incorrect:
B. Authentication policy with 'known-user' selected:
This would only apply to users the firewall has already identified. It would not work for a new, unauthenticated BYOD device.
C & D. Security policy with 'known-user' or 'unknown' selected:
A Security policy is used to permit or deny traffic based on applications, users, and zones. While a security policy can be based on user identity, it doesn't trigger the authentication process itself. The authentication policy is what initiates the user's identification.

References:
Palo Alto Networks: User Identification and Authentication

Palo Alto Networks: Best Practices

A. Navigate to Objects > Security Profiles > Anti-Spyware Select related profile Select DNS exceptions tabs Search related threat ID and click enable Commit

Explanation:

The threat log indicates:
Threat Type: Spyware
Category: dns-c2 (DNS command-and-control)
Threat ID: 1000011111
This means the detection was triggered by the Anti-Spyware profile, specifically targeting DNS-based C2 activity. To create an exception for this signature, the administrator must modify the Anti-Spyware profile.

Steps to configure the exception:
Go to Objects > Security Profiles > Anti-Spyware
Select the relevant Anti-Spyware profile
Navigate to the Exceptions tab
Click Show All Signatures
Search for Threat ID 1000011111
Click Enable to allow editing
Modify the action (e.g., alert instead of block)
Commit the changes
📚 Reference:
Palo Alto Networks – Configure Anti-Spyware Exceptions

❌ Why Other Options Are Wrong:
A. Incorrect — DNS exceptions tab is for domain-based exceptions, not threat ID-based signature exceptions.
B & C. Incorrect — Vulnerability Protection profiles do not handle spyware or DNS-C2 signatures.

D. Create custom vulnerability signatures manually in Panorama, and push them to the firewalls

Explanation:
Panorama provides centralized management for custom vulnerability signatures (also known as "threat signatures"). To deploy multiple signatures quickly across all perimeter firewalls:
Create signatures in Panorama: Navigate to Objects > Custom Signatures in Panorama. Here, you can manually define the dozen+ signatures requested by the threat intelligence team.
Push to firewalls: Once created, these custom signatures are part of Panorama's shared objects. They can be pushed to all managed firewalls simultaneously through a standard policy commit from Panorama.
This approach is the most efficient because it avoids repetitive manual configuration on each firewall and leverages Panorama's central management capability.

Why the Other Options Are Incorrect:
A. Use Expedition:
Expedition is a migration tool for converting configurations from other vendors to PAN-OS. It is not designed for creating or deploying custom threat signatures.
B. Create manually on one firewall and export/import:
This is time-consuming and error-prone. It requires manual export/import for each firewall, which is inefficient for a large fleet.
C. Use Panorama IPS Signature Converter:
This tool converts signatures from other formats (e.g., Snort) to PAN-OS format. It is not for creating new custom signatures from scratch based on a team's request.

Reference:
PAN-OS documentation recommends using Panorama for centralized custom signature management to ensure consistency and reduce deployment time (PAN-OS Administrator’s Guide, "Custom Signatures" section). Signatures created in Panorama are pushed to all associated firewalls during a commit.

A. Choose the URL categories in the User Credential Submission column and set action to block Select the User credential Detection tab and select Use Domain Credential Filter Commit

Explanation:
A network administrator aims to prevent domain username and password submissions to phishing sites within allowed URL categories on a Palo Alto Networks firewall. The URL Filtering profile, configured under Objects > Security Profiles > URL Filtering, includes features to detect and block credential submissions to untrusted or phishing sites. The User Credential Submission column allows the administrator to select specific URL categories (e.g., "Phishing," "Malware") and set the action to "block" to prevent credential entry on those sites. The User Credential Detection tab enables the firewall to identify domain credentials using the Domain Credential Filter, which integrates with User-ID to monitor and block submissions of Active Directory credentials to unauthorized sites. This combination ensures protection while allowing legitimate traffic.

Why Other Options Are Incorrect:
B. Choose the URL categories in the User Credential Submission column and set action to block, Select the User credential Detection tab and select use IP User Mapping, Commit: This is incorrect because IP User Mapping maps users to IPs but does not specifically detect or filter domain credentials. The Domain Credential Filter is required for credential-specific protection. The PCNSE Study Guide clarifies the distinction.
C. Choose the URL categories on Site Access column and set action to block, Click the User credential Detection tab and select IP User Mapping, Commit: This is incorrect because the Site Access column controls general access (allow/deny) to URL categories, not credential submission specifically. IP User Mapping is irrelevant here, and the correct column is User Credential Submission. The PAN-OS 11.1 Administrator’s Guide specifies the correct column.
D. Choose the URL categories in the User Credential Submission column and set action to block, Select the URL filtering settings and enable Domain Credential Filter, Commit: This is incorrect because there is no URL Filtering Settings tab to enable the Domain Credential Filter; it is configured under the User Credential Detection tab. The PCNSE Study Guide confirms the correct tab.

Practical Steps:
Navigate to Objects > Security Profiles > URL Filtering.
Create or edit a URL Filtering profile.
In the User Credential Submission column, select the relevant URL categories (e.g., "Phishing") and set the action to "block".
Go to the User Credential Detection tab, check Use Domain Credential Filter.
Ensure User-ID is configured with an Active Directory connection under Device > User
Identification.
Attach the profile to a Security policy under Policies > Security.
Commit the configuration.
Verify via Monitor > Threat Logs that credential submissions are blocked.

References:
Palo Alto Networks PAN-OS 11.1 Administrator’s Guide: Details URL Filtering for credential protection.
Palo Alto Networks PCNSE Study Guide: Explains credential submission settings.