Typical IT infrastructure has seven domains

A typical IT infrastructure has seven domains: User Domain, Workstation Domain, LAN Domain, LAN-to-WAN Domain, WAN Domain, Remote Access Domain, and System/Application Domain. Each domain requires proper security controls that must meet the requirements of confidentiality, integrity, and availability. Answer the following question(s): In your opinion, which domain is the most difficult to monitor for malicious activity? Why? In your opinion, which domain is the most difficult to protect? Why?