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.
- Dradis v2.9 – Information Sharing For Security Assessments
- MagicTree v1.3 Available For Download – Pentesting Productivity
- Kvasir – Penetration Testing Data Management Tool
- 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) - 1,135,991 views
- Hack Tools/Exploits - 579,467 views
- Password Cracking with Rainbowcrack and Rainbow Tables - 413,260 views