Prevention rate is the share of tested malicious activity that security controls successfully block. It is a practical measure of how well defenses interrupt attack behavior, not just whether tools are installed or alerts are generated. A high prevention rate suggests that controls can stop more of the actions an attacker needs to continue.
This metric matters because attackers often rely on evasion, living-off-the-land techniques, and small changes in execution to slip past detection. In real defenses, prevention rate is used to validate endpoint, network, and email controls against realistic attack paths. Low results usually signal gaps in coverage, poor tuning, or weak response to specific techniques, while higher results show stronger interruption of malicious activity before it becomes a breach.