How to Read Basic Firewall Log

Firewall is a network security devices or software that controls and monitoring incoming and outgoing network traffic based on predetermined security rules. Its primary purpose is to establish a barrier between a trusted internal network and untrusted external networks, such as the internet and prevent threats by blocking malicious traffic from entering or exiting a network. Firewalls can prevent unauthorized access to or from a private network, helping to protect sensitive data and systems.

Basic firewall log records various details about network traffic that has been processed by the firewall. Here are some common elements typically found in a firewall log:

Sample Traffic Allowed

Timestamp: 2099-12-11 10:15:30
Source IP: 192.168.192.2
Destination IP: 10.20.30.5
Source Port: 54321
Destination Port: 443
Protocol: TCP
Action: ALLOWED
Rule ID: 666
Bytes Sent: 500
Bytes Received: 1200
Session ID: 56780

Explanation of the Log Fields:

Timestamp: The date and time when the event was logged.

• Source IP Address: The IP address of the device that initiated the connection.
• Destination IP Address: The IP address of the device that received the connection.
• Source Port: The port number on the source device that is being used.
• Destination Port: The port number on the destination device that is being accessed.
• Protocol: The protocol being used for the connection, such as TCP, UDP, or ICMP.
• Action Taken: Indicates whether the traffic was allowed or blocked by the firewall.
• Rule ID: A reference to the specific rule in the firewall configuration that triggered the log entry.
• Bytes Sent/Received: The amount of data sent or received during the connection.
• Session ID: A unique identifier for the specific session.

Sample Traffic Blocked

Date       Time        Source IP       Source Port  Destination IP    Destination Port  Protocol  Action    Reason
05/05/2045 05:50:55   192.168.192.10    52345        10.0.0.10         22                TCP       BLOCK     Access Denied - Policy Violation

Explanation of the Log Fields:

• Date: The date of the logged event.
• Time: The time the event occurred.
• Source IP: The IP address of the device that initiated the connection.
• Source Port: The port number on the source device used for the connection.
• Destination IP: The IP address of the target device attempting to be accessed.
• Destination Port: The port number on the target device (e.g., SSH uses port 22).
• Protocol: The protocol used for the connection (e.g., TCP, UDP).
• Action: The action taken by the firewall (e.g., BLOCK or ALLOW).
• Reason: The justification for the action taken, typically based on predefined firewall rules.

This log entry indicates that a device with the IP address 192.168.192.10 attempted to connect to the web server at 10.0.0.10, but the firewall blocked the request due to a policy violation.

Firewall logs provide several key benefits for network security and management:

• Threat Detection: Logs help in identifying unauthorized access attempts and suspicious activities by monitoring traffic patterns and alerting administrators about potential threats.
• Incident Response: In the event of a security breach, firewall logs can provide crucial information for analyzing how the breach occurred, which systems were affected, and what data was accessed.
• Compliance and Auditing: Many industries have regulatory requirements for data protection. Firewall logs support compliance by offering a record of network access, helping organizations demonstrate adherence to security standards.
• Performance Monitoring: Logs can reveal bandwidth usage and performance issues, helping in optimizing network resources and ensuring that services are running efficiently.
• User Activity Monitoring: They provide insights into user behavior on the network, which can inform security policies, training needs, and overall network management strategies.
• Troubleshooting: When network some issues, logs can assist in diagnosing problems by detailing traffic flow and packet abnormalities, facilitating quicker resolution of issues.
• Forensic Analysis: In the case of a cybersecurity incident, logs serve as an important artifact for forensic investigation to understand the timeline and methods used in the attack.

By leveraging firewall logs effectively, organizations can enhance their security posture and improve their overall infrastructure security & network management.