What is Secure Boot?
Secure Boot checks what starts before Windows really loads. If something early in the boot process is not signed correctly, the system should reject it.
This matters because pre-OS attacks are especially difficult. If malicious code runs before Windows, normal protection can arrive too late.
What exactly expires?
Microsoft says some devices still use 2011 Secure Boot certificates. The target is a move to 2023 Secure Boot certificates.
If a device is not updated, Windows does not necessarily stop working immediately, but Secure Boot may not be able to validate future updates to early boot components. That is serious enough not to leave until the last minute.
Where can businesses feel the problem?
The unpleasant scenario is a laptop asking for a BitLocker recovery key on Monday morning, while nobody knows where that key is stored. Another scenario is firmware or boot trouble after a late update.
Older laptops and desktops, rarely used machines, devices outside the office and BitLocker-enabled computers deserve special attention.
What should be checked?
First: device inventory. Second: firmware updates from the manufacturer. Third: a pilot group before broad rollout. Fourth: BitLocker recovery keys. Fifth: documentation of what was checked and on which device.
For Dell, HP, Lenovo, ASUS, Acer and other manufacturers, firmware updates are often not the same as ordinary Windows updates. This work should be planned, not improvised.
Conclusion
Secure Boot certificates are not a glamorous topic, but they matter. This is the kind of IT work nobody notices when it is done on time, and everyone notices when it is not.
It is better to spend an hour checking than to lose half a day because a laptop will not boot or asks for a BitLocker key during work.