Windows defender is blocking almost all app's

Question

After the latest update Windows defender is blocking all non and some microsoft apps.

When I start an app from my quickstart it shows the message:"These files can't be opened"

If I try to start any app's from the start menu, it just does not respond.There are no records of blocking any app's in the protection history.

• I can get acces to Microsoft edge and part of the settings. I can not install or uninstall anything.- turning off the tamper protection does not help- turning off Real-time protection does not help- turning off cloud-deliverd protection does not help- I can not start gpedit.msc, to block the defender.- I can not empty the scans dir., because I do not get access to the dir. I am logged in as an administrator: c:\programdata\microsoft\windows defender\scans\history- I can only run the windows virusscanner, other programs will not start or can not be installed- Ccleaner will not start- I tried to reset the pc, but the system encounters an unknown error and just rebooted.- An advanced start-up does not help.- turning off the firewall does not help

The windows system is up to date (Windows 10 version 22h2) and is a legal version.

I did find a way to start firefox by opening a pdf file as a website.Also I can open my thunderbird, when I open a saved email.Also it is possible to open files, I can move them, copy then and delete them.

Do you guys have any other ideas how I could solve this?

Info about pc:

Device name JCSL
Processor AMD Ryzen 5 2600 Six-Core Processor 3.40 GHz
Installed RAM 16,0 GB
Device ID 291AB8A4-57E6-415D-9885-2AD76906F407
Product ID 00331-20300-00000-AA473
System type 64-bit operating system, x64-based processor
Pen and touch No pen or touch input is available for this display

Edition Windows 10 Pro
Version 21H2
Installed on ‎08/‎09/‎2020
OS build 19044.3086
Experience Windows Feature Experience Pack 1000.19041.1000.0

Answer 1

Thanks for posting your question in the Microsoft Q&A forum.
I'd consider using System Restore to revert the system to a point before the latest update and be sure that the update is the source of the problem.

Also, you can use the Windows Defender Offline Scan. This scan runs outside of Windows and might detect and remove malware that could be causing issues.

** Please don't forget to close up the thread here by upvoting and accept it as an answer if it is helpful **

Answer 2

Hi,

Is there any change before the problem happens? Such as software installation, system, or file scanning, setting change. Undo the change if possible and check the result.

If you have the local admin account, try to create a new local account and log on system using the new account to check the result. To confirm that if it is caused by corrupted user profile.

Create a local user or administrator account in Windows:

https://support.microsoft.com/en-us/windows/create-a-local-user-or-administrator-account-in-windows-20de74e0-ac7f-3502-a866-32915af2a34d

Besides, we may try repair install/upgrade to scan and repair system files.

Perform a Repair Upgrade Using the Windows 11 or Windows 10 ISO file:

https://answers.microsoft.com/en-us/windows/forum/all/how-to-perform-a-repair-upgrade-using-the-windows/35160fbe-9352-4e70-9887-f40096ec3085