To update a signature in Windows Defender:
Select the Start button, select Settings > Update & security > Windows Defender > Open Windows Defender.
Select the Update tab.
Select the Update definitions button.
If Windows Defender finds a new signature, it will download and install it.
The update completes with the new signature. Keep these points in mind.
Note: that if you get an error message while trying to download or update a signature, you can wait for at least one hour and try again or update signatures manually.
Also, make sure the signature you want to download is 50 MB or larger to ensure you get the complete signature file.
Article ID: 4027712 - Last Review: 2017, ജൂലൈ 29 - Revision: 1