To protect a VoIP infrastructure against a denial-of-service (DoS) attack, it is MOST important to
secure the:

A.
access control servers.

B.
session border controllers.

C.
backbone gateways.

D.
intrusion detection system (IDS).

Explanation:
Session border controllers enhance the security in the access network and in the core. In the access
network, they hide a user’s real address and provide a managed public address. This public address
can be monitored, minimizing the opportunities forscanning and denial-of-service ( DoS ) attacks.
Session border controllers permit access to clients behind firewalls while maintaining the firewall’s
effectiveness. In the core, session border controllers protect the users and the network. They hide
network topology and users’ real addresses. They can also monitor bandwidth and quality of service.
Securing the access control server, backbone gateways and intrusion detection systems (IDSs) does
not effectively protect against DoS attacks.