Coverage validation is the process of testing whether a security control or detection rule actually fires when it sees known malicious behavior. In detection engineering, it is not enough to write a rule that looks correct on paper; teams must confirm that the data source, parsing, logic, and alerting path all work end to end.
This matters because a detection can appear complete while missing key attacker techniques, producing false confidence. Coverage validation helps defenders find blind spots in endpoint, identity, cloud, or network telemetry and check whether a rule maps to the behavior it claims to detect. In practice, teams validate coverage by replaying test events, using adversary emulation, or running controlled simulations against ATT&CK techniques. That makes coverage validation a core part of building reliable alerts, tuning noisy rules, and proving that defenses can actually observe malicious activity.