What is War Dialing?

What is War Dialing?

A.
War dialing involves the use of a program in conjunction with a modem to penetrate the modem/PBX-based systems

B.
War dialing is a vulnerability scanning technique that penetrates Firewalls

C.
It is a social engineering technique that uses Phone calls to trick victims

D.
Involves IDS Scanning Fragments to bypass Internet filters and stateful Firewalls