When configuring a security device to ensure that, in the event of a failure, it will maintain a state that prevents traffic from passing through it, which mode should be used?
Fail-closed mode is used in security devices to ensure that if the device fails, it does not allow any traffic through, thereby maintaining the security posture by default. This contrasts with fail-open mode, where the device would allow all traffic through in the event of a failure, potentially compromising security.