To scan a USB drive with Windows Defender, select it in a Windows Security custom scan. You can also use the drive’s right-click scan option when it is available. You do not need to edit the registry to scan one memory stick.
Scan the USB stick through Windows Security
- Connect a drive you trust without opening unfamiliar files. Avoid connecting an unknown USB device you found in public.
- Open Windows Security → Virus & threat protection.
- Open Scan options, choose Custom scan and select Scan now.
- Choose the USB drive or the folder you want to check. Confirm its drive letter in File Explorer first.
- Wait for the scan to finish and review the result.
In File Explorer, you may be able to right-click the drive and select Scan with Microsoft Defender. On Windows 11, look under Show more options if needed. If the command is missing, use Windows Security and check which antivirus provider is active.
Which scan should you use for a memory stick?
| Scan or protection | What it means for the USB drive |
|---|---|
| Custom scan | You choose the USB drive or folder. This is the direct way to check its contents. |
| Quick scan | Checks common places where malware starts. Do not treat it as a complete check of every file on the USB stick. |
| Real-time protection | Checks covered files as you access them; it is not proof that the entire stick was scanned on connection. |
| Full scan | Removable-drive inclusion depends on the separate scan setting or policy. |
Microsoft’s scan-type guide recommends a custom scan for checking a portable device. Its Defender policy documentation explains the full-scan removable-drive setting.
Tips for using Microsoft Defender on USB drives
- Update Defender’s security information before scanning when possible.
- Keep real-time protection on if Defender is your active antivirus.
- Scan before copying files you do not know or running an installer from the drive.
- Do not add the whole USB drive as an antivirus exclusion to silence a warning.
- Keep a separate backup of important files; a scan is not a backup.
Optional: scan the USB drive with PowerShell
On a compatible Defender setup, an administrator can use Start-MpScan. Replace E:\ below with the actual drive letter:
Start-MpScan -ScanType CustomScan -ScanPath "E:\"This is a PowerShell command. A work or school PC may have managed settings; ask its administrator instead of trying to override them.
What should you do after the scan?
Open Protection history to review any alert and the action Defender took. Use our Defender quarantine guide to understand those results. Do not restore an unknown file simply to make it open.
If a download is blocked, see how to check a virus-detected warning. A scan with no detections reduces risk, but does not guarantee that every file or the USB hardware itself is safe.
Updated October 14, 2026. Instructions and available features can vary by device, account and software version.