Hao is a network security engineer for a mid-sized company. She is redesigning the infrastructure and its resources to provide greater protection from both external and internal threats. She wants to place firewall devices not only where the local area network (LAN) connects to the Internet, but also within the network. Although she doesn't suspect any employees of misusing computer resources, there is always the potential that one might send unauthorized emails or other messages containing confidential company information to a competitor. Which redundant solution should she select that will be most likely to detect malicious behavior by an internal employee