Common Log Sources: Firewalls, IDS/IPS, Servers, and Endpoints

In the world of cybersecurity, logs are like digital footprints. Every action, whether it’s a user login, a file being accessed, or a network packet being transferred, leaves behind a record. These records—called logs—help organizations track what’s happening inside their systems and networks.

Logs are extremely important for detecting threats, troubleshooting issues, and meeting compliance requirements. But not all logs are the same. They come from different sources, and each type provides a unique perspective on security.

In this blog, we’ll explore the common log sources you’re likely to encounter: firewalls, IDS/IPS, servers, and endpoints. We’ll break them down in simple terms so that even beginners can understand why they matter.

• Firewall Logs

A firewall acts as the security guard of your network. It decides which traffic can come in, which can go out, and which should be blocked. Think of it as the bouncer at a club—only the right people get in.

Firewall logs record everything the firewall sees and does. Some key details you’ll find in these logs include:

• Allowed and blocked traffic – Which IP addresses are trying to connect and whether they succeeded.
• Port usage – Information about what services (like HTTP on port 80 or HTTPS on port 443) are being used.
• Protocols – Whether the traffic is TCP, UDP, ICMP, etc.
• Connection attempts – Failed and successful attempts to reach your systems.

Why firewall logs matter?

They give security teams a clear picture of potential attacks, such as port scanning, brute force attempts, or denial-of-service (DoS) attacks. Reviewing firewall logs helps organizations block malicious IPs and spot unusual traffic patterns.

• IDS/IPS Logs

IDS (Intrusion Detection System) and IPS (Intrusion Prevention System) go a step beyond firewalls. While firewalls enforce rules, IDS/IPS look deeper into the actual traffic to detect suspicious activities.

• IDS is like a CCTV camera—it watches and alerts when something suspicious happens.
• IPS is like a security guard—it not only alerts but also blocks malicious activities.

IDS/IPS logs usually contain:

• Signatures of attacks (e.g., SQL injection, malware, or brute force attempts).
• Alerts of suspicious patterns such as repeated failed login attempts.
• Preventive actions (in IPS) where malicious traffic was blocked automatically.

Why IDS/IPS logs matter?

They provide detailed insight into active attacks. Security analysts use these logs to identify ongoing threats, investigate how attackers operate, and strengthen defenses. For example, if a hacker tries to exploit a vulnerability in your system, IDS/IPS logs will likely flag it.

• Server Logs

Servers are the heart of IT infrastructure. Whether it’s a web server, database server, or application server, they generate logs that are critical for both security and performance monitoring.

There are different types of server logs:

• System logs – Record system-level events like startup, shutdown, errors, and warnings.
• Application logs – Show what applications are doing, such as user activities or application errors.
• Web server logs – Track website visits, HTTP requests, response codes, and IP addresses of visitors.
• Database logs – Capture queries, failed access attempts, and data changes.

 Why server logs matter?

They provide the first line of evidence when something goes wrong. For example:

• If a website is slow, server logs can show whether it’s due to traffic overload or errors.
• If a hacker tries SQL injection, web server logs will often show suspicious queries.
• If unauthorized access happens, system logs can reveal login details.

In short, server logs help detect both operational issues and security incidents.

• Endpoint Logs

Endpoints are devices used by end-users—like laptops, desktops, and mobile phones. Since attackers often target endpoints as entry points into networks, endpoint logs are crucial.

Common endpoint logs include:

• Antivirus/EDR logs – Show detected malware, quarantined files, or blocked actions.
• Authentication logs – Track login attempts and password failures.
• System health logs – Monitor updates, patches, and system errors.
• User activity logs – Record actions like file access, USB usage, or software installations.

Why endpoint logs matter?

Endpoints are often the weakest link in security because people use them every day. If an employee clicks a phishing email, endpoint logs will show whether malware was executed. If ransomware starts encrypting files, EDR (Endpoint Detection and Response) logs can detect and stop it before it spreads.

How Logs Work Together

It’s important to understand that no single log source tells the full story. Instead, they complement each other:

• Firewall logs may show that traffic came from a suspicious IP.
• IDS/IPS logs may confirm that the traffic contained malicious payloads.
• Server logs may reveal that the attack successfully reached an application.
• Endpoint logs may show that malware was finally executed on a user’s laptop.

By combining logs from all these sources, organizations get a complete picture of what’s happening. This is why tools like SIEM (Security Information and Event Management) exist—they collect logs from multiple sources and help security teams detect and respond to threats faster.

Challenges with Logs

While logs are powerful, managing them comes with challenges:

• Too many logs – Large organizations generate millions of log entries every day.
• Noise vs. useful data – Not all logs are important; filtering is necessary.
• Storage issues – Keeping logs for compliance and analysis can be costly.
• Correlation – Logs from different systems must be analyzed together for context.

This is why log management solutions and SIEM platforms are so valuable—they automate collection, filtering, and analysis.

Conclusion

Logs are the backbone of cybersecurity monitoring. They act as the digital “black box” of an organization, recording everything from network traffic to user actions. By focusing on firewall logs, IDS/IPS logs, server logs, and endpoint logs, security teams can detect threats, investigate incidents, and keep systems running smoothly.

When these log sources are combined, they provide a powerful defense against cyberattacks. The key is not just collecting logs but analyzing and correlating them effectively to see the bigger picture.

In today’s threat landscape, understanding and using logs wisely isn’t just a technical task—it’s a business necessity.