[whatupmiked]

There is no evidence secure boot has prevented any malware.

[mjg59]

There are UEFI bootkits in the wild that are prevented by secure boot.

[whatupmiked]

An attack that does not work on a technology is not evidence of a control’s effectiveness.

[mjg59]

Literally the only difference between a system with secure boot and one without is that unsigned boot components (such as the ones used by prior UEFI bootkits) won't boot. The fact that they don't work is absolutely evidence of the effectiveness of the control.