Understanding Firewall Logs: Basics and Best Practices

Firewalls are the first line of defense in any cybersecurity setup. Thus, familiarizing with firewall logs is a breakthrough for security surveillance and log examination. So if you’re new to this, don’t freak out. So I’m here to give you the basics in a friendly and accessible way.

What Are Firewall Logs?

Imagine firewall logs as your firewall’s diary. Each time it blocks or permits traffic, it records the details. These logs reveal what types of data packets are flowing through, from where, and if anything seemed fishy.

• Everything that flows to your firewall is being logged.
• Indicate whether each connection is allowed or denied.
• Assist in hunting down anomalous or adversarial behavior.

You can identify potential threats before they escalate into a large issue by regularly reviewing these logs.

Key Log Components

A firewall log entry is like a report — when you read an entry you have opened. But some parts are more important than the others. Let’s unpack the main elements for you:

• Timestamp: When information did the event occur?
  • Always your starting point.
• Sourced IP Address: What is the origin of the traffic?
  • Useful for investigating suspicious or unknown IPs.
• Destination IP Address: Where was the traffic going?
  • You need to assess whether internal systems are at risk.
• Protocol: What type of communication?
  • Commonly TCP, UDP, or ICMP.
• Port Number: What service was used?
  • Web traffic typically goes to 80 or 443, for example.
• What did the firewall do? Allow, Block?
  • Essential for catching denial suspicious attempts.
• Which rule (Policy) triggered the action?
  • Informs you about traffic allowed or blocked.

Put these together, and you get a complete story of what’s happening on the network.

Interpreting Log Messages

Logs are simply uncontexted data as of now. Here’s how you can read between the lines of what they really mean:

• Start with Action Taken. If it was blocked, that’s a good sign for that instance, but what caused it to be blocked?
• Check the Source IP. Is it from a trusted network, or somewhere mysterious?
• Look at Protocol and Port. Odd ports or unexpected protocols might suggest probing or attacks.
• Make Sure You Understand the Rule You Are Applying. Does firewall have a special policy for such traffic?
• All duplicate entries from that IP where they tried to connect again and again. It may well be a brute force or scanning attack.

Now, some of the entries are just normal traffic so don’t jump to conclusions. But patterns or unfamiliar sources merit more scrutiny.

Detecting Suspicious Behavior

Well, here’s where you get to be a detective. You are looking for threats early on by reading clues in the log.

Watch out for:

• Several unsuccessful tries in a short time from the same IP. This could also indicate that someone is trying to crack passwords or scan your network.
• Unusual traffic from geolocations your business isn’t based in.
• Even some type of anomalous traffic / ports trying to use non-standard ports.
• Sudden increase in outbound traffic flowing to unknown destinations – may suggest data exfiltration.
• Frequent hits on sensitive ports, such as SSH (port 22) or RDP (port 3389).

If you encounter any of these, tag them for more detailed examination or trigger an alert.

Best Practices

By efficiently managing firewall logs, security monitoring and log analysis gets ahead of the game.

• Automate Log Collection: Use centralized logging tools to aggregate log information from all your firewalls.
• Define Your Baseline: Understand typical network activities, so you can spot odd behaviors more easily.
• Schedule Regular Reviews: Logs can accumulate rapidly. Depending on your risk profile, schedule daily or weekly reviews.
• Make use of filters and alerts: Filter the noise and set alerts for key suspicious activities.
• Secure the Logs: Prevent the log from being altered or accessed by an unauthorized party.
• Powering Up with Other Security Tools: Correlate logs with SIEM, or endpoint security to get a clearer security view.
• Train Your Team: Ensure staff know how to monitor logs and what to do.

If you follow these, your firewall logs turn from data debris to a front line security weapon.

All firewall logs are a necessity for proper security monitoring and log analysis. They uncover hidden dangers within your network. So, learn them and use them wisely. We all have to start somewhere, and practice makes reading a firewall logs second nature. Keep poking, keep learning, and stay safe out there!