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I have a PC with an Asus motherboard running Windows 7 Pro. Yesterday I installed latest Windows updates, restarted, and shortly afterwards hibernated the machine.
This morning on un-hibernating I got a black screen with:
The system found unauthorized changes on the firmware,operating system or UEFI drivers
It also said:
Go to BIOS Setup > Advanced > Boot and change the current boot device into other secured boot devices
The only way I was able to get it to boot was by changing the BIOS secure boot OS to 'other OS' i.e. I think this means secure boot is effectively disabled.
There have been no hardware changes to this machine recently (last thing I changed was adding more RAM about 3 weeks ago, and it has successfully rebooted multiple times since then). There is no CD/DVD or bootable USB device connected.
I'm running a full MSE scan just to be sure / paranoid. Is it possible the Windows updates caused this? Should I be concerned about disabling secure boot? I've tried setting it back to enabled however the original message reappears.
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Can't answer because of reputation, but likely that this was caused by optional Windows update KB3133977 which was a recently released Bitlocker fix (2016/03/14) that affects boot files: https://support.microsoft.com/en-gb/kb/3133977 and would change the signature, leading to the warning. If that's the case, this would be benign.
People reporting it tend to have ASUS motherboards: sources https://hardforum.com/threads/secure-boot-suddenly-stopped-working-with-windows-7.1894722/ and http://www.sevenforums.com/system-security/393432-help-uefi-bios-os-compromised.html
And you can apparently fix it without disabling Secure Boot (though as mentioned that's not officially supported) in the BIOS by System Restore from a previous backup, then not installing KB3133977. – Steven Maude – 2016-04-11T19:26:56.483
(searching for KB3133977) this thread https://hardforum.com/threads/secure-boot-suddenly-stopped-working-with-windows-7.1894722/#post-1042205964 seems to suggest ASUS are using a non-standard secure boot implementation...
– Nick Baker – 2016-04-12T08:23:11.573'Microsoft has been in touch to say: