Microsoft Defender Antivirus

Microsoft Defender Antivirus is the antivirus built into Windows 10 and 11. It scans files in real time, gets cloud-delivered protection and daily security intelligence updates, and is managed in the Windows Security app. When another antivirus is installed and registered, Defender switches its real-time protection off automatically.

1Scan types

A quick scan checks the places where malware usually runs. A full scan checks all files and can take more than an hour. A custom scan checks chosen files or folders. Microsoft Defender Offline scan restarts the PC and scans before Windows starts, which helps against malware that hides while Windows runs.

2Protection history and quarantine

Windows Security > Virus & threat protection > Protection history lists detections and actions. Quarantined files are kept in a safe place and can be restored or removed from there.

3Command line

MpCmdRun.exe in C:\Program Files\Windows Defender runs scans and updates from the command line, for example MpCmdRun.exe -Scan -ScanType 1 for a quick scan. In PowerShell, 'Start-MpScan' and 'Update-MpSignature' do the same.

How to run a full or offline scan

1. Open Windows Security > Virus & threat protection.
2. Select Scan options.
3. Choose Full scan, or Microsoft Defender Offline scan if you suspect hidden malware.
4. Select Scan now. The offline scan restarts the PC and takes about 15 minutes.
5. Afterwards, check Protection history for the result.

Related articles

• Microsoft Defender SmartScreenWhat SmartScreen is, why it shows 'Windows protected your PC' for new downloads, and how to check a file before running it.
• Startup appsWhere Windows lists the programs that start with it, what the startup impact means, and how to turn startup apps off safely.
• Event ViewerHow to read Windows event logs in Event Viewer, which logs matter for crashes and errors, and how to export or clear them.

Sources

1. Stay protected with Windows Security (Microsoft Support) support.microsoft.com
2. Use the command line to manage Microsoft Defender Antivirus (Microsoft Learn) learn.microsoft.com

Note: Rain Cleaner is not an antivirus; its ransomware protection works alongside Microsoft Defender.

Last reviewed: 2026-10-08