Which of the following is a technique for gathering information about a remote network protected
by a firewall?

A.
Firewalking

B.
Warchalking

C.
War driving

D.
War dialing

Explanation:

Fire walking is a technique for gathering information about a remote network protected by a
firewall. This technique can be used effectively to perform information gathering attacks. In this
technique, an attacker sends a crafted packet with a TTL value that is set to expire one hop past
the firewall. If the firewall allows this crafted packet through, it forwards the packet to the next hop.
On the next hop, the packet expires and elicits an ICMP “TTL expired in transit” message to the
attacker. If the firewall does not allow the traffic, there should be no response, or an ICMP
“administratively prohibited” message should be returned to the attacker. A malicious attacker can
use firewalking to determine the types of ports/protocols that can bypass the firewall. To use
firewalking, the attacker needs the IP address of the last known gateway before the firewall and
the IP address of a host located behind the firewall. The main drawback of this technique is that if
an administrator blocks ICMP packets from leaving the network, it is ineffective.
Answer option B is incorrect. Warchalking is the drawing of symbols in public places to advertise
an open Wi-Fi wireless network. Having found a Wi-Fi node, the warchalker draws a special
symbol on a nearby object, such as a wall, the pavement, or a lamp post. The name warchalking
is derived from the cracker terms war dialing and war driving.
Answer option C is incorrect. War driving, also called access point mapping, is the act of locating
and possibly exploiting connections to wireless local area networks while driving around a city or
elsewhere. To do war driving, one needs a vehicle, a computer (which can be a laptop), a wireless
Ethernet card set to work in promiscuous mode, and some kind of an antenna which can be
mounted on top of or positioned inside the car. Because a wireless LAN may have a range that
extends beyond an office building, an outside user may be able to intrude into the network, obtain
a free Internet connection, and possibly gain access to company records and other resources.
Answer option D is incorrect. War dialing or wardialing is a technique of using a modem to

automatically scan a list of telephone numbers, usually dialing every number in a local area code
to search for computers, Bulletin board systems, and fax machines. Hackers use the resulting lists
for various purposes, hobbyists for exploration, and crackers – hackers that specialize in computer
security – for password guessing.