Manual Reference Pages - FIREWALK (8)
firewalk - Active Reconnaissance Network Security Tool with Extreme Prejudice
firewalk [-dhinprSsTtvx] target_gateway metric
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
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. Please see http://www.wiley.com/cda/product/0,,0471205443,00.html
for more information on Firewalking and networking security tools in general.
If an option takes an argument, it procedes the option letter, with the
default in parenthesis.
-d 1-65535 (34434) ||
Specify the initial destination port to use during the network discovery
(aka TTL ramping) phase.
-i interface_name ||
Specify interface to use. Only neccessary on multi-homed machines.
Do not resolve IP addresses into hostnames. This saves a DNS lookup
and speeds the scans (mainly during network discovery).
-P 1-2000 (0) ||
Set a network writing pause which may be neccessary to keep the program from
flooding the network.
-p TCP, UDP (UDP) ||
Type of scan to perform.
Strict RFC 793 compliance. This only comes into play when doing a TCP scan
when your packets have an expire vector of one and your metric host is one
hop from your gateway. Since the packets will reach their destination, they
will not expire, so we look for terminal responses. For a TCP port in the
listen state, we will get back a SYN|ACK with the ACK as our SEQ + 1. However,
for a closed port, the response is stack dependent. If the host is RFC
compliant we will receive an RST|ACK with the ACK as our SEQ + 1. However,
if the host is not compliant (ie: microsoft) then the best we can do is
inverse tuple matching (which is the default).
-S 1-65535,... (1-130,139,1025) |
Specify the ports for the scan. Ports may be specified in ranges, delimited by
dashes, and multiple ranges may be specified, delimited by commas. Ommiting
the terminating port number is shorthand for 65535.
-s 1-65535 (53) ||
Specify the source port for the scan (both phases).
-T 1-2000 (2) ||
Network packet reading timeout. This is the time firewalk will spend
waiting for a response before timing out.
-t 1-25 (1) ||
Set the initial IP time to live (TTL) value. If a target gateway is known
to be (at least) n hops from the source host, the TTL can be preloaded to
facilitate a faster scan.
Dump program version and exit.
-x expire vector (1) |
The expire vector is the number of hops that the scanning probes will
expire, past the gateway host. The binding hopcount is the hopcount of the
gateway + the expire vector.
traceroute(8), tracerx(8), pcap(3), libnet(3), dnet(3)
Mike D. Schiffman <firstname.lastname@example.org>
Please send bug reports to email@example.com
|firewalk ||FIREWALK (8) ||04.20.2002 |
Visit the GSP FreeBSD Man Page Interface.
Output converted with manServer 1.07.