An external attacker has compromised an organization’s network security perimeter and installed a sniffer onto an inside computer. Which of the following is the MOST effective layer of security the organization could have implemented to mitigate the attacker’s ability to gain further information?

A. Implement packet filtering on the network firewalls
B. Install Host Based Intrusion Detection Systems (HIDS)
C. Require strong authentication for administrators
D. Implement logical network segmentation at the switches