Firewalk

Prinzip

Man schickt ein TCP oder UDP mit einem Port den man checken will durch eine FIREWALL mit einer reduzierten TTL. Wird dann ein "ICMP time exceeded" zurück gesendet, weiss man das dieser Port in der FIREWALL freigeschaltet ist.

Manuell

Port geschlossen

• traceroute -m 3 -T -p 888 8.8.8.8

traceroute to 8.8.8.8 (8.8.8.8), 3 hops max, 60 byte packets
 1  _gateway (10.81.0.1)  104.850 ms  208.596 ms *
 2  worf.xinux.lan (10.80.0.2)  215.199 ms  215.147 ms  215.037 ms
 3  * * *

Port offen

• traceroute -m 3 -T -p 777 8.8.8.8

traceroute to 8.8.8.8 (8.8.8.8), 3 hops max, 60 byte packets
 1  * * *
 2  worf.xinux.lan (10.80.0.2)  0.336 ms  0.254 ms  0.331 ms
 3  217.5.XX.18 (217.5.XX.18)  17.895 ms  18.754 ms  18.636 ms

Firewalk

Port offen

• firewalk -S 777 -i eth0 -n -pTCP 10.80.0.2 8.8.8.8

Firewalk 5.0 [gateway ACL scanner]
Firewalk state initialization completed successfully.
TCP-based scan.
Ramping phase source port: 53, destination port: 33434
Hotfoot through 10.80.0.2 using 8.8.8.8 as a metric.
Ramping Phase:
 1 (TTL  1): expired [10.81.0.1]
 2 (TTL  2): expired [10.80.0.2]
Binding host reached.
Scan bound at 3 hops.
Scanning Phase: 
port 777: open (expired) [217.5.XX.18]

Scan completed successfully.

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

Port geschlossen

• firewalk -S 888 -i eth0 -n -pTCP 10.80.0.2 8.8.8.8

Firewalk 5.0 [gateway ACL scanner]
Firewalk state initialization completed successfully.
TCP-based scan.
Ramping phase source port: 53, destination port: 33434
Hotfoot through 10.80.0.2 using 8.8.8.8 as a metric.
Ramping Phase:
 1 (TTL  1): expired [10.81.0.1]
 2 (TTL  2): expired [10.80.0.2]
Binding host reached.
Scan bound at 3 hops.
Scanning Phase: 
port 888: *no response*

Scan completed successfully.

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