An important control that should be in place for external connections to a network that uses callback schemes is:

A.
Call enhancement

B.
Breaking of a dial-up connection at the organization’s computing resource side of the line

C.
Breaking of a dial-up connection at the remote user’s side of the line

D.
Call forwarding

Explanation:
One attack that can be applied when call back is used for remote, dial-up connections is that the
caller may not hang up. If the caller had been previously authenticated and has completed his/her
session, a live connection into the remote network will still be maintained. Also, an unauthenticated
remote user may hold the line open, acting as if call-back authentication has taken place. Thus, an
active disconnect should be effected at the computing resource’s side of the line. Answer “Breaking
of a dial-up connection at the remote user’s side of the line” is not correct since it involves the caller

hanging up. Answer “call forwarding” is a feature that should be disabled, if possible, when used
with call-back schemes. With call back, a cracker can have a call forwarded from a valid phone
number to an invalid phone number during the call-back process. Answer “Call enhancement” is a
distracter.