Tips and Tricks: Firewall Logs in Cyber Forensics and Incident Response

Just as with traditional investigations, cyber forensics and incident response rely on accurate and detailed data, and when it comes to security investigations, nothing fits the bill quite like firewall logs. Those logs become your best friends if you ever find yourself dealing with a cyber attack. They tell stories about what took place, how it transpired and sometimes even who’s responsible.

Logs And Their Role In Incident Response

Let’s start with the basics. The first step in the event of a security breach is incident response. Firewall logs are the diary of your network’s security posture. They log each packet that attempts to enter or leave as well as successful and blocked attempts.

Why are these logs so useful?

• Timeline of events: You can see precisely when the attack began.
• What was targeted: IPs or services under attack?
• Assist in isolating affected systems: Find out where the breach has occurred.

Logs give you clues early on. Without them, you’d be flying blind, trying to figure out what went wrong.

Identifying Attack Vectors

One of the hardest aspects of a security investigation is determining the attack vector — how the attacker penetrated or attempted to reach your systems. Firewall logs are an integral part of this, recording all incoming and outgoing connections.

So here’s how firewall logs combat attack vectors:

• Raising alerts for unusual traffic patterns: Such as peaks of connections from a single IP.
• Expose blocked versus allowed traffic: You can see which attacks were successful.
• Protocols and ports targeted: Helpful for detecting scans or exploits.

Studying data points like this, you begin to learn the attacker’s technique. For example:

• Was it a brute force attack on SSH?
• Was a web service exploited that was vulnerable?
• Or perhaps a questionable DNS query?

Understanding how the breach began informs what you do next.

Tracking Malicious Activity

Once you know how the attack began, tracking what the attacker did is vital. These help trace movement of external attackers as communication attempts are made between external attackers and internal devices, which is visible in firewall logs.

Here’s what to watch for:

• Repeated, frantic attempts to access things: Attackers often try to access things repeatedly before they break in.
• Phone home to suspicious IP addresses: These can be command-and-control servers.
• Abnormal external communications: Potential sign of data exfiltration.

The logs essentially allow you to follow the attacker’s footprints. You can see whether they attempted lateral movement throughout the network or whether they just stayed hot in one system.

Correlating Logs with SIEM

Firewall logs are very important data, but even better when we throw in a Security Information and Event Management (SIEM) solution to the mix.

SIEM tools collect and analyze logs from multiple sources — firewalls, servers, endpoints — for a complete perspective.

Why it benefits to correlate firewall logs with SIEM

• Automated identification of potential threats: Notifies you if abnormal behavior occurs
• Comprehensive incident timelines: Understand how various logs can link to the same threat.
• Unified context across investigations: Discover user behavior correlations and system events.

You’re also accelerating investigations and minimizing blind spots when you feed firewall data into a SIEM.

How to Write an Investigation Report

Finally, after gathering firewall logs and analyzing them you’ll need to write a clearly defined investigation report.

Here’s what to include:

• Brief overview of the incident: what happened and when
• Attack vector details: The means by which the attacker gained access
• Timeline of malicious activity — what they did inside your network.
• Affected systems: (Compromised systems); (Data affected)
• Advice on mitigation: Patching, blocking IPs, and tightening firewall rules

While this can get rather lengthy, this step is very important, as it makes your report easy to follow. Make it lists, timelines, visuals if you’re able. Keep in mind that, depending on the use of the document, it might be read by executives or other teams, so eliminate jargon when possible.

Wrapping Up

Tips and Tricks: Firewall Logs in Cyber Forensics and Incident Response

Firewall logs – these are an event log created by the firewall to log security or event-related information. FW logs are a plenty and an invaluable lot when it comes to cyber forensics or incident response. They also help identify attack vectors, track malicious activities and serve up data that in conjunction with SIEM enables faster, better security investigations.

When faced with a security breach, don’t wait: see what those firewall logs can tell you early on. They’re often the secret to understanding exactly what went wrong and how to correct it.

In practice, nothing caters better than the fine-grained logs from your firewalls for cyber forensics, incident response, and security investigations.