is a security strategy that applies multiple layers of defense because there is an assumption that any single protection mechanism in the environment will fail at some point.

Layered security

Explanation:

Layered security is a multiple layers defense practice used to protect resources and data. One goal of the layered security is to create redundancies or also known as backups to face the situation that one or more of the security measures in the outer layer fail or are bypassed, at least the resources and data still get protected by inner layer security. The number of security layer set for the resources is dependent on how important the resources are.

that would be my answer.