Firewalk – Firewall Ruleset Testing Tool

Use Netsparker


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:

firewalk.tar.gz

Or read more here.

Posted in: Hacking News

, , ,


Latest Posts:


Eraser - Windows Secure Erase Hard Drive Wiper Eraser – Windows Secure Erase Hard Drive Wiper
Eraser is a hard drive wiper for Windows which allows you to run a secure erase and completely remove sensitive data from your hard drive by overwriting it several times with carefully selected patterns.
Insecure software versions are a problem Web Security Stats Show XSS & Outdated Software Are Major Problems
Netsparker just published some anonymized Web Security Stats about the security vulnerabilities their online solution identified on their users’ web applications and web services during the last 3 years.
CTFR - Abuse Certificate Transparency Logs For HTTPS Subdomains CTFR – Abuse Certificate Transparency Logs For HTTPS Subdomains
CTFR is a Python-based tool to Abuse Certificate Transparency Logs to get subdomains from a HTTPS website in a few seconds.
testssl.sh - Test SSL Security Including Ciphers, Protocols & Detect Flaws testssl.sh – Test SSL Security Including Ciphers, Protocols & Detect Flaws
testssl.sh is a free command line tool to test SSL security, it checks a server's service on any port for the support of TLS/SSL ciphers, protocols as well as recent cryptographic flaws and more.
Four Year Old libSSH Bug Leaves Servers Wide Open Four Year Old libssh Bug Leaves Servers Wide Open
A fairly serious 4-year old libssh bug has left servers vulnerable to remote compromise, fortunately, the attack surface isn't that big as neither OpenSSH or the GitHub implementation are affected.
CHIPSEC - Platform Security Assessment Framework CHIPSEC – Platform Security Assessment Framework For Firmware Hacking
CHIPSEC is a platform security assessment framework for PCs including hardware, system firmware (BIOS/UEFI), and platform components for firmware hacking.


2 Responses to Firewalk – Firewall Ruleset Testing Tool

  1. navin October 15, 2008 at 10:21 am #

    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 October 17, 2008 at 4:00 pm #

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