The best metric to demonstrate that servers are configured securely is the total number of servers meeting the baseline for hardening. Hardening is the process of applying security configurations and settings to servers to reduce their attack surface and vulnerability. A baseline is a standard or benchmark that defines the minimum level of security required for servers. By measuring the number of servers that meet the baseline, the organization can assess the effectiveness of its hardening efforts and identify any gaps or deviations. The other metrics, such as exceeding availability thresholds, experiencing hardware failures, or exceeding current patching standards, are not directly related to the security configuration of servers, but rather to their performance, reliability, or maintenance. References = Risk and Information Systems Control Study Manual, Chapter 2, Section 2.3.2, page 2-25.