firewalk Usage Example

Scan ports 8079-8081 (-S8079-8081) through the eth0 interface (-i eth0), do not resolve hostnames (-n), use TCP (-pTCP) via the gateway ( against the target IP (

[email protected]:~# firewalk -S8079-8081  -i eth0 -n -pTCP
Firewalk 5.0 [gateway ACL scanner]
Firewalk state initialization completed successfully.
TCP-based scan.
Ramping phase source port: 53, destination port: 33434
Hotfoot through using as a metric.
Ramping Phase:
 1 (TTL  1): expired []
Binding host reached.
Scan bound at 2 hops.
Scanning Phase:
port 8079: *no response*
port 8080: A! open (port not listen) []
port 8081: *no response*

Scan completed successfully.

Total packets sent:                4
Total packet errors:               0
Total packets caught               2
Total packets caught of interest   2
Total ports scanned                3
Total ports open:                  1
Total ports unknown:               0

Packages and Binaries:


Firewalk is an active reconnaissance network security tool that attempts to determine what layer 4 protocols a given IP forwarding device will pass. It works by sending out TCP or UDP packets with a TTL one hop 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. Otherwise, it will likely drop the packets and there will be no response.

To get the correct IP TTL that will result in packets expiring one hop beyond the gateway, Firewalk needs to ramp up hop counts. It does this in the same manner that traceroute works. Once the scan is bound (that is, Firewalk knows the gateway hop count), it begins the scan. The ultimate destination host does not have to be reached, it only needs to be somewhere downstream, on the other side of the gateway, from the scanning host.

Firewalk helps in assessing the security configuration of packet filtering devices, such as those used in firewall systems. It is relevant for network security assessments, like network penetration tests (pentests).

Installed size: 50 KB
How to install: sudo apt install firewalk

  • libc6
  • libdumbnet1
  • libnet1
  • libpcap0.8

Active Reconnaissance Network Security Tool with Extreme Prejudice

[email protected]:~# firewalk --help
firewalk: invalid option -- '-'
Usage : firewalk [options] target_gateway metric
		   [-d 0 - 65535] destination port to use (ramping phase)
		   [-h] program help
		   [-i device] interface
		   [-n] do not resolve IP addresses into hostnames
		   [-p TCP | UDP] firewalk protocol
		   [-r] strict RFC adherence
		   [-S x - y, z] port range to scan
		   [-s 0 - 65535] source port
		   [-T 1 - 1000] packet read timeout in ms
		   [-t 1 - 25] IP time to live
		   [-v] program version
		   [-x 1 - 8] expire vector

Updated on: 2022-May-04