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 for scanning 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.