Which of the following countermeasures would be the most appropriate to prevent possible intrusion or damage
from wardialing attacks?

A.
Monitoring and auditing for such activity

B.
Require user authentication

C.
Making sure only necessary phone numbers are made public

D.
Using completely different numbers for voice and data accesses

Explanation:
War dialing 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 – malicious hackers who
specialize in computer security – for guessing user accounts (by capturing voicemail greetings), or locating
modems that might provide an entry-point into computer or other electronic systems. It may also be used by
security personnel, for example, to detect unauthorized devices, such as modems or faxes, on a company’s
telephone network.
To prevent possible intrusion or damage from wardialing attacks, you should configure the system to require
authentication before a network connection can be established. This will ensure that an attacker cannot gain
access to the network without knowing a username and password.
Incorrect Answers:
A: Monitoring wardialing attacks would not prevent an attacker gaining access to the network. It would just tell
you that at attack has happened.C: Making sure only necessary phone numbers are made public will not protect against intrusion. An attacker
would still be able to gain access through one of the ‘necessary’ phone numbers.
D: Using completely different numbers for voice and data accesses will not protect against intrusion. An
attacker would still be able to gain access through one of the data access phone numbers.

http://en.wikipedia.org/wiki/War_dialing