15 October 2008 | 14,975 views

Firewalk – Firewall Ruleset Testing Tool

Check Your Web Security with Acunetix

This is another oldskool tool, but still relevant! TCP and UDP still work in the same way and firewalls/edge devices are still often configured wrongly.

Firewalk is an active reconnaissance network security tool that attempts to determine what layer 4 protocols a given IP forwarding device will pass. Firewalk works by sending out TCP or UDP packets with a TTL one greater than the targeted gateway. If the gateway allows the traffic, it will forward the packets to the next hop where they will expire and elicit an ICMP_TIME_EXCEEDED message. If the gateway hostdoes not allow the traffic, it will likely drop the packets on the floor and we will see no response.

To get the correct IP TTL that will result in expired packets one beyond the gateway we need to ramp up hop-counts. We do this in the same manner that traceroute works. Once we have the gateway hopcount (at that point the scan is said to be bound) we can begin our scan.

It is significant to note the fact that the ultimate destination host does not have to be reached. It just needs to be somewhere downstream, on the other side of the gateway, from the scanning host.

Read the original 1998 whitepaper here.

You can download Firewalk here:


Or read more here.


Recent in General Hacking:
- Drones, Tor & Remailers – The Story Of A High-Tech Kidnapping
- U.S. State Department Hacked
- Kali Linux – The Most Advanced Penetration Testing Linux Distribution

Related Posts:
- FWAuto v1.1 – Firewall Auditing & Ruleset Analyzer Tool
- Dr. Morena – Firewall Configuration Testing Tool
- FTester – Firewall Tester and IDS Testing tool

Most Read in General Hacking:
- 10 Best Security Live CD Distros (Pen-Test, Forensics & Recovery) - 1,158,768 views
- Hack Tools/Exploits - 609,344 views
- Password Cracking with Rainbowcrack and Rainbow Tables - 427,367 views

Advertise on Darknet

2 Responses to “Firewalk – Firewall Ruleset Testing Tool”

  1. navin 15 October 2008 at 10:21 am Permalink

    i don’t get it….whts so unknown abt it?? don’t all network recon tools work in the same way?? I mean the n+1 TTL ?? I mean atleast tht’s how I think they mostly work…am I right??

  2. Anonymoose 17 October 2008 at 4:00 pm Permalink

    That’s the point! It’s an old-school tool that still works.