Defender Quickscan

Defender Quick Scan

Trigger Windows Defender antivirus scans, inspect threat history, update virus definitions, and check real-time protection status — all via PowerShell cmdlets.

When to Use

• User wants to run a quick or full antivirus scan
• User asks about recent threats detected by Defender
• User wants to check if real-time protection is enabled
• User needs to update virus/malware signatures
• User wants to know the current Defender protection status

How to Use

Check Windows Defender status

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Get-MpComputerStatus | Select-Object AMServiceEnabled, AntispywareEnabled,
  AntivirusEnabled, RealTimeProtectionEnabled,
  AntispywareSignatureAge, AntivirusSignatureAge, QuickScanAge

Run a quick or full scan

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Start-MpScan -ScanType QuickScan   # fast scan of likely threat locations
Start-MpScan -ScanType FullScan    # thorough scan of all files (30-60 min)

Scan a specific file or folder

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Start-MpScan -ScanType CustomScan -ScanPath "C:\Users\<you>\Downloads"

Update virus definitions

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Update-MpSignature

View threat detection history

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Get-MpThreatDetection | Select-Object ThreatID, ActionSuccess,
  DetectionSourceTypeID, Resources, InitialDetectionTime |
  Sort-Object InitialDetectionTime -Descending |
  Select-Object -First 10

View active threats

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Get-MpThreat | Select-Object ThreatID, ThreatName, SeverityID,
  CategoryID, IsActive, Resources

Remove a detected threat

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Remove-MpThreat -ThreatID 12345

Check exclusion list

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(Get-MpPreference).ExclusionPath
(Get-MpPreference).ExclusionExtension

Add a scan exclusion (path)

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Add-MpPreference -ExclusionPath "C:\DevTools\node_modules"

Examples

"Scan my Downloads folder for threats" → Start-MpScan -ScanType CustomScan -ScanPath "$env:USERPROFILE\Downloads" — Defender scans the folder and logs any detections.

"Are my virus definitions up to date?" → Get-MpComputerStatus | Select-Object AntivirusSignatureAge, AntivirusSignatureLastUpdated — signature age of 0 means updated today.

"Show me the last 5 threats Defender found" → Get-MpThreatDetection | Sort-Object InitialDetectionTime -Descending | Select-Object -First 5

Cautions

• Full scans can take 30-60 minutes and consume significant CPU/IO — warn the user before running
• Start-MpScan requires Windows Defender to be the active antivirus — third-party AV may disable these cmdlets
• Removing a threat with Remove-MpThreat is permanent; confirm with the user before executing
• Adding exclusions reduces protection coverage — only exclude paths you're certain are safe