Palo Alto Networks NGFW Log Analysis and Operational Requirements

In Palo Alto Networks Next-Generation Firewalls (NGFW), log analysis serves as the foundation for network visibility, troubleshooting, and security incident response. This article defines the structure of the multi-faceted log data generated by the NGFW and explains efficient analysis methods and technical operational requirements in practice.

1. Log Architecture Classification and Definition

Palo Alto Networks NGFW identifies traffic behavior using multi-dimensional contexts such as App-ID, User-ID, and Content-ID, and records them categorized as follows.

A. Traffic Log

Session-based communication records and the most frequently referenced logs. They record source/destination IP, application, port number, applied security policy, and action (Allow/Deny/Drop/Reset).

B. Threat Log

Records events detected by security profiles, such as antivirus, spyware, vulnerability protection (IPS), and C2 (Command & Control) communications. These play a central role in forensics during incident response.

C. URL Filtering Log

Records web browsing activity in detail. Includes accessed URLs, categories (SNS, malicious sites, etc.), and user identification information.

D. WildFire Log

Records the results of unknown file analysis by the cloud sandbox. It maintains file names, SHA-256 hashes, and analysis results (Benign, Malicious, Grayware, Phishing), contributing to the detection of zero-day attacks.

E. Data Filtering Log

Related to DLP (Data Loss Prevention) functions, this monitors and records attempts to leak sensitive information (such as credit card numbers or personal identification numbers) externally.

F. System Log

Records the operational status of the device itself. This includes administrator login history, configuration changes (Commit), interface Up/Down status, and license renewal status.

2. Traffic Analysis Workflow in Practice

When connectivity issues occur, administrators filter logs using the following steps to identify the cause.

1. Navigate to Monitor > Logs > Traffic.
2. Execute Filtering: Extract logs related to a specific source IP address (e.g., 10.10.10.100).
3. Verify Action: Check the Action column to determine if the traffic is being rejected (Deny) by a policy or permitted (Allow).

3. Leveraging Advanced Filtering Syntax

For efficient analysis, mastering the filtering syntax available in both the CLI and WebUI is essential. Practical syntax examples:

( addr.src in 10.10.10.100 ) and ( port.dst eq 443 )
( app eq web-browsing ) and ( action eq deny )
( zone.src eq 'Trust' ) and ( zone.dst eq 'Untrust' )
( severity eq critical ) or ( severity eq high )

4. Session Analysis via Detailed Log View

By viewing log entries in the Detailed Log View, retrievable metadata includes:

• Zone Information: Source and destination security zones.
• NAT Translation: IP and port after source/destination NAT (essential for verifying NAT policy inconsistencies).
• Session ID: An ID that uniquely identifies a specific flow.
• Applied Rule Name: The specific security policy name that controlled the communication.
• Counters: Total bytes and packets transferred.

5. Technical Operational Considerations and Maintaining Consistency

To ensure log reliability and retention periods, the following settings must be observed.

Thorough NTP Synchronization

If the Network Time Protocol (NTP) is not synchronized, discrepancies will occur in log timestamps, making correlation analysis impossible. It is mandatory to reference a common time source across all devices.

Log at Session End

In security policy settings, “Log at Session End” must be enabled. Recording only at the start of a session results in missing data for transferred bytes and session duration.

Log Retention and External Forwarding

Since the physical storage capacity of the device is limited, the retention period must be designed according to traffic volume. If long-term storage or integrated management is required, configure forwarding to Panorama (centralized management platform) or an external Syslog server.

User-ID Mapping Verification

It is necessary to periodically monitor the status of User-ID agents to ensure that the mapping between IP addresses and usernames is performed accurately.

Summary

Log analysis in Palo Alto Networks NGFW is not merely a means of post-event verification, but a process directly linked to validating policy validity and maintaining network health. By understanding the characteristics of each log category—such as Traffic, Threat, URL, and System—and utilizing appropriate filtering syntax, rapid troubleshooting and robust security operations become possible. In particular, NTP synchronization and “Log at Session End” settings are essential requirements for maintaining data integrity.