Windows Defender update: So secure, it wouldn't let Secure-Boot Windows PCs, er, boot

It has been a trying time for Microsoft punters after a Windows Defender update left some PCs unable to boot last week, while other folk continue to struggle to even get to the update service.

How do you make a PC super secure? Don't let it boot

A tweak to Windows Defender slowly creeping its way over PCs has an issue that can stop Windows 10 booting (and a few iterations of Windows Server - Microsoft points to Server 2016, but some users have reported problems with Server 2019).

Some admins have been in rollback city as dozens of users found their workstations unbootable.

Tech author and blogger Günter Born took a look at the issue, and by the end of last week Microsoft had confirmed that there was a problem with the Windows Defender update and made a swift tweak to the issues list.

While problems with downloads being blocked due to a change in the file path location in the update have been known about for a while, that some Secure Boot-enabled Windows 10 PCs would fail to boot came as a surprise.

The issue results in affected Windows 10 PCs (or Windows Servers) not being able to start following a reboot. Microsoft's solution? Dive into the machine's BIOS and, er, disable that whole pesky Secure Boot thing.

Once back in Windows, Microsoft has provided users with commands to be run from a handy admin command prompt to stop Windows Defender pointing at the borked binary: 4.18.1901.7. Secure Boot can then be switched back on.

The gang at Redmond said they were working on the issue and plan to release a fix "in a future update", but gave no time frame.

Thanks to an eagle-eyed anonymous Reg reader for the tip.

Where, oh where has my Windows Update gone?

Some users may not have received the Windows Defender update at all as the service became inaccessible for a number of customers anxiously awaiting the next dollop of steaming goodness to drop from Redmond's update orifice.

Comcast customers in the US were the first to begin squeaking about the problem, filling the company's boards with complaints. Some users reported that manually switching to a different DNS provider appeared to cure the ill, hinting at something being amiss with Comcast's infrastructure.

The Register approached Comcast for comment and, while it did not respond to us, the issue was apparently quietly resolved.

However, because anything those pesky Americans can do, plucky Brits can do better, customers of UK telecoms giant BT also began reporting problems at the end of last week as the ISP protected users from downloading 1809 experienced symptoms similar to those of Comcast.

A forum posting with 130 messages at time of writing indicates that all is not well on this side of the pond for some customers. Like the Comcast problem, users have had some success after fiddling with their DNS settings, but other than confirming the issue was being investigated, BT has remained tight-lipped.

The Register contacted BT to find out if it had anything to say on the matter but has yet to receive a response. A Redditor claiming to be a Microsoft engineer also posted, stating that the Windows giant was aware of the issue and would report back but Microsoft hasn't responded to our requests for comment.

While enterprising users have reported success with switching to Google's DNS, some remain unable to connect to the Windows Update service. And those virus definitions will getting a bit old by now. ®

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