To reduce the attack surface of a system, administrators should perform which of the following processes to remove unnecessary software, services, and insecure configuration settings?

Harvesting is a reconnaissance technique used by attackers to collect email addresses, credentials, or data from targets, and is not a defensive configuration process.

Windowing is not a recognized information security process for reducing attack surfaces - it relates to networking concepts or UI paradigms.

Hardening is a well-defined security practice in which administrators systematically eliminate unnecessary attack vectors - including unneeded network services, unused software packages, default credentials, and weak configuration settings. By reducing the number of entry points and vulnerabilities present on a system, hardening directly lowers the risk of compromise and is a foundational element of both CIS Benchmarks and NIST security guidance.

Stealthing refers to techniques for concealing a system or its open ports from discovery, and does not involve removing unnecessary software or reconfiguring insecure settings.