A risk practitioner is defining metrics for security threats that were not identified by antivirus...

A KRI is a measure used by an organization to measure the health of a particular risk. In this case, the risk practitioner is developing a metric to measure the risk associated with security threats that were not identified by antivirus software12.

References

1Standardized Scoring for Security and Risk Metrics - ISACA

2Key Performance Indicators for Security Governance, Part 1 - ISACA