Hello
Thank you for your question and reaching out. I can understand you are having query\issues related to Defender.
Please note that associated event IDs are :
Windows Defender scan has started. (Event ID 1000)
Windows Defender scan has finished. (Event ID 1001)
Windows Defender signature version has been updated. (2000)
Also please check this path : C:\Windows\Microsoft Antimalware\Support and C:\ProgramData\Microsoft\Windows Defender\Offline Scanner
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