Which of the following is a key performance indicator (KPI) for measuring the efficiency of patch management?
Patch SLA compliance percentage is a primary key performance indicator (KPI) because it directly measures how effectively the IT and security teams meet established service-level agreement deadlines for deploying updates. By tracking the percentage of systems patched within the mandated window (e.g., critical patches within 72 hours), organizations can quantitatively evaluate the efficiency and consistency of their vulnerability management lifecycle.
Why this answer
Patch SLA compliance % directly measures how efficiently the patch management process meets its defined service-level targets — the percentage of patches applied within the agreed remediation window. This is a process-efficiency KPI because it evaluates the speed and consistency of the patching workflow against a defined benchmark. MTTR measures incident response, not patch throughput, and open vulnerability count reflects exposure rather than process efficiency.
Exam trap
CS0-004 often tests the distinction between process-efficiency KPIs (SLA compliance, patch cycle time) and outcome/risk metrics (open vulnerabilities, MTTR), so candidates who grab the most 'security-sounding' metric pick the wrong answer.
How to eliminate wrong answers
Option A is wrong because MTTR (mean time to respond) is an incident-response metric that measures how quickly security teams react to incidents, not how efficiently patches are deployed. Option B is wrong because the number of open vulnerabilities is a risk/exposure metric — it can rise or fall for reasons unrelated to patch process efficiency (new scans, new CVEs, false positives). Option C is wrong because phishing simulation click rate measures security awareness training effectiveness, which is unrelated to patch management.