In the modern digital world, cyber threats evolve faster than ever, making advanced network scanning techniques crucial for organizations. One technique that often confuses beginners is what is firewalking in cyber security, a method used by ethical hackers and penetration testers to map the behavior of firewalls and routers. Understanding this technique is essential for strengthening network defense, closing security gaps, and preventing unauthorized access.
This article explains what is firewalking in cyber security in simple, clear, and actionable language so anyone—from students to IT professionals—can understand how it works, why attackers use it, and how organizations can defend against it.
What Is Firewalking in Cyber Security? (Simple Definition)
To put it simply, firewalking is a reconnaissance technique used to identify which ports and services a firewall allows or denies. When asking what is firewalking in cyber security, think of it as a method to “walk” through a firewall by sending specific packets and analyzing their responses.
Firewalking helps security professionals:
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Discover firewall rules
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Identify open and closed ports
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Map network paths
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Understand how traffic flows through routers
Attackers may also use firewalking to plan targeted attacks, which is why understanding what is firewalking in cyber security is crucial for defense.
How Firewalking Works (Step-by-Step Explanation)
One of the most important parts of understanding what is firewalking in cyber security is learning how the technique actually functions. The concept is based on TTL (Time-To-Live) values in packets.
Here’s how firewalking typically works:
1. Determine the Gateway
The tester first identifies the gateway or firewall controlling traffic. This is usually done with traceroute.
2. Send Probes with Specific TTL Values
Packets are sent with a TTL set to expire exactly at the gateway.
3. Analyze the Firewall’s Behavior
If the firewall allows the packet, it will forward it, and it will expire one hop later, sending an ICMP “TTL expired” message back.
If the firewall blocks the port, the packet will never reach the next hop.
4. Build a Port Map
By sending packets to different ports, testers can learn:
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Which ports the firewall allows
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Which ports it blocks
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Whether filtering rules exist
This ability to map allowed traffic is why what is firewalking in cyber security is considered a powerful reconnaissance technique.
Why Firewalking Is Used in Cyber Security
There are several reasons why firewalking is valuable:
1. Testing Firewall Rules
Cybersecurity teams use firewalking to verify whether firewall configurations match security policies.
2. Identifying Misconfigurations
Incorrect firewall settings can expose networks. Firewalking helps spot:
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Accidental open ports
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Weak filtering rules
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Dangerous access pathways
3. Planning Security Improvements
Understanding what is firewalking in cyber security allows organizations to strengthen defenses by adjusting firewall rules or tightening access controls.
4. Penetration Testing & Ethical Hacking
Firewalking is a common step in the reconnaissance phase of penetration tests, helping professionals simulate real-world attacks.
Firewalking vs. Other Scanning Techniques
To fully understand what is firewalking in cyber security, it helps to compare it with other common scanning tools.
Firewalking vs. Port Scanning
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Port scanning identifies open ports directly.
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Firewalking identifies which ports a firewall allows through.
Firewalking vs. Traceroute
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Traceroute maps network paths.
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Firewalking maps which ports the firewall filters along that path.
Firewalking vs. Ping Sweeps
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Ping sweeps identify live hosts.
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Firewalking identifies firewall behavior and filtering rules.
Firewalking is more advanced because it reveals how a firewall behaves under specific conditions—not just what is open or closed.
How to Prevent Firewalking Attacks
Security experts who understand what is firewalking in cyber security also know how to defend against it. The best practices include:
1. Block ICMP Error Messages
Limiting ICMP responses makes it harder for attackers to analyze TTL-based packet behavior.
2. Use Stateful Firewalls
Stateful inspection prevents unauthorized traffic from passing through simply because the port appears open.
3. Filter Traffic Strictly
Only permit traffic that is absolutely necessary for business operations.
4. Regular Firewall Audits
Routine audits help identify misconfigurations before attackers do.
5. IDS/IPS Monitoring
Intrusion detection and prevention systems can alert administrators to suspicious scanning activity.
Conclusion
If you were wondering what is firewalking in cyber security, the answer is clear: it is a powerful reconnaissance technique used to analyze firewall rules, discover allowed ports, and understand how a network filters traffic. While attackers might use firewalking for malicious purposes, cybersecurity professionals use it to strengthen defenses, identify vulnerabilities, and ensure proper firewall configuration.
With cyber threats increasing daily, mastering techniques like firewalking is essential for protecting networks and maintaining strong security posture.
FAQs
1. What is firewalking in cyber security?
Firewalking is a network reconnaissance technique used to identify which ports and services a firewall allows or blocks.
2. How does firewalking work?
It works by sending packets with specific TTL values and analyzing the firewall’s response to determine filtering rules.
3. Why do hackers use firewalking?
Hackers use firewalking to map firewall rules and discover potential entry points for attacks.
4. Is firewalking legal?
Yes, but only when performed by authorized cybersecurity professionals during penetration testing.
5. How can organizations prevent firewalking attacks?
They can block ICMP error messages, use stateful firewalls, apply strict traffic filtering, and monitor networks with IDS/IPS tools.