Scan your PC with Microsoft Defender (including offline)

A full scan, then an offline scan for persistent threats.

1. Update the signatures first (PowerShell):

   Update-MpSignature

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2. Start a full scan:

   Start-MpScan -ScanType FullScan

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3. Graphical interface: Windows Security → Virus & threat protection → Scan options.
4. If you suspect malware hiding while Windows runs, choose "Microsoft Defender Offline scan": the PC restarts and scans before the system loads.
5. The offline scan can also be started from the command line:

   Start-MpWDOSScan

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6. Then check the protection history to see what was quarantined.