This works in most cases, where the issue is originated due to a system corruption.
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To manually install the latest Windows Defender definitions from the Microsoft website The first and simplest method that usually helps with error 0x80070643 in this case is to download the definitions of Windows Defender from the Microsoft website and install them manually. Go to https:// and go to the Manually download and install the definitions section.Type cd /d “\Program Files\Windows Defender” into the Command Prompt and press the Enter key.Type exe -signatureupdate into the Command Prompt and press the Enter key.Right-click on the Start Menu button to open the Win X Menu.In the Win X Menu, click on Command Prompt (Admin) to open an elevated Command Prompt.If you choose to participate, the online survey will be presented to you when you leave the Msdn Web site. One of the possible errors that a Windows 10 user may encounter is the message “Update definition for Windows Defender KB_NUM_RESOLUTION – error 0x80070643” in the update center.NOTE: Whenever Windows Defender, Microsoft Security Essentials, Malicious Software Removal Tool, or System Center Endpoint Protection detects a malware, it will restore the following system settings and services which the malware might have changed: The Windows Defender client update failed.This event occurs when the client fails to update itself.Fortunately, there are a multitude of different viable solutions for this problem, and the following are the three most effective solutions that you can use to get rid of this issue: If you have been trying to update Windows Defender from the program itself and failing because of “connectivity problems”, the most logical solution for the issue would certainly be trying to update Windows Defender using Windows Update. As soon as the available updates for Windows Defender are detected, they will automatically start being downloaded. If the issue is with your computer or a laptop/notebook you should try using the Reimage Plus Software which can scan the repositories and replace corrupt and missing files.