The correct answer is C - Device hardening.
WGU Cybersecurity Architecture and Engineering (KFO1 / D488) teaches that device hardening involves reducing vulnerabilities by disabling unnecessary services, ports, and features. Closing unneeded network ports minimizes the attack surface and strengthens device security.
An intrusion prevention system (A) monitors and blocks threats but does not close ports directly. A web application firewall (B) protects web apps, not device configurations. An intrusion detection system (D) only alerts but does not proactively secure devices.
Reference Extract from Study Guide:
"Device hardening minimizes vulnerabilities by disabling unnecessary services and ports, securing the system against network-based attacks."
- WGU Cybersecurity Architecture and Engineering (KFO1 / D488), Device Hardening and Secure Configuration