What are firewall logs and why they are important

Network setups of the past consisted solely of servers in a server closet. Today, modern IT infrastructure consists of three main components: on-premises data centers, public clouds, and their connecting infrastructure.

This new reality has created complex systems with multiple challenges.

Regulations have become stricter, and organizations are under pressure to detect security threats fast. When faced with an issue, network security professionals must pinpoint the root cause, and to do that, they need evidence—which means investigating firewall logs.

A firewall log is a record of the network connections (allowed and blocked) that a firewall inspects, capturing each event between your systems and the internet. 

Depending on the configuration, a firewall log may include all inspected traffic or only what the firewall allows to pass into the environment (what “gets past” the firewall).

Each entry of a firewall log will specify the following data:

Beyond the question of “What is a firewall log?” there is also the question of where to store them. Organizations have a few options here.

Firewall logs can:

• Stay on the firewall device

• Go to a basic syslog server for storage

• Undergo analysis via a security information and event management (SIEM) tool

The process of reviewing a firewall is akin to a scheduled maintenance procedure that updates the rulebook of your firewall system. 

Things to be on the lookout for include:

• Duplicate rules

• Outdated server rules

• Overly broad rules that can lead to security vulnerabilities

Ready to play detective? Because a firewall log review requires just that. 

Analyzing firewall data is a continuous process of extracting relevant information from the firewall logs, i.e., the firewall’s own journal of events.. 

The key is to identify specific patterns that indicate security incidents, performance issues, or non-compliance events. 

This, in turn, requires centralizing logs with synchronized device clocks so that timelines line up (i.e., NTP across firewalls, servers, and your SIEM) and putting controls in place to preserve log integrity.

So now that it is clear what a firewall log is—as well as how to store these logs and review them—the next step is knowing how to interpret them. 

Successfully extracting the necessary data from your firewall logs is a six-step process:

1. Collect logs in one place: The central system needs to receive logs from all firewalls that extend from the data center to the cloud. Each entry missing from your logs allows malicious actors to remain unseen, i.e., pose an unknown threat..

2. Figure out what's normal: To detect abnormal behavior, you must first create a baseline for normal activity, i.e., typical traffic patterns.

3. Hunt for suspicious patterns: The official investigation begins! What to flag? Network scanning activity from a single IP address that attempts to access multiple ports and internal devices and makes scheduled connections to unverified external servers (beaconing).

4. Add context: Context turns raw events into decisions. Enrich IPs and ports from your logs with: 

   1. Asset inventory: What system and business app is this?

   2. User directories: Who owns/uses it?

   3. Threat intelligence: Is the source/destination risky? 

This enrichment helps determine impact and priority—not just “who/what,” but whether

the activity is expected, whether the system is critical, and how urgently you need to

respond.

5. Investigate and act: Trigger an incident response plan: 

   1. Validate findings

   2. Contain the incident (isolate the host, block indicators at the firewall).

   3. Collect forensics (packet captures, memory snapshot, log preservation) 

   4. Eradicate the threat

   5. Recover systems, operations, and data (patches, credential resets, rule updates)

   6. Notify stakeholders

   7. Document the case for post‑incident review.

Measure and improve: Learn from your results. Identify rules that are creating too much noise and clean them up. Most importantly, track how long it takes you to respond to incidents you find in your logs.

Firewall log management across hybrid environments requires more than manual monitoring. It demands contextual understanding, automated processes, and permanent security measures. 

AlgoSec offers multiple features to combine all these components. It empowers your team to not only fully grasp what firewall logs are and their importance, but also helps you transition from event analysis to evidence-based remediation:

• AlgoSec Horizon: Security policy management via an approach based on business application, not a specific device. Offers complete monitoring of app connections between data centers and clouds, automated policy updates, and continuous compliance monitoring, connecting log traffic to actual application operations. 

• Firewall Analyzer: Complete visibility into all firewalls to detect dangerous or unneeded rules. Optimizes rule bases by focusing on essential risk-related elements, resulting in less log data, improved signal quality, and faster review processes. 

• FireFlow: Issue detection and response based on log data. Leverages automated workflows to execute risk and compliance assessments pre-deployment, complete with documentation; integrates with current ITSM systems (e.g., ServiceNow, BMC Remedy) so teams can perform change management tasks within a familiar environment. 

• AlgoSec Cloud Enterprise (ACE): A single policy framework for cloud and hybrid systems. Enables automated security group and cloud firewall rule management; performs 150+ cloud policy risk checks to deliver application-specific insights from cloud logs. 

Now is the time to convert your firewall logs into valuable business decisions. Request a demo to see AlgoSec in action today.