Microsoft Defender (formerly Windows Defender) is built into Windows 10 and Windows 11 and provides real-time protection against security threats. While it runs automatically in the background, you can manually initiate scans to check your system for viruses, malware, and other potentially harmful software.

Accessing Microsoft Defender

There are several ways to open Microsoft Defender:

Method 1: Using Windows Security

1. Click the Start button.
2. Select Settings (gear icon).
3. Click on Privacy & Security (Windows 11) or Update & Security (Windows 10).
4. Select Windows Security.
5. Click on Virus & threat protection.

Method 2: Using Search

1. Press Windows key on your keyboard.
2. Type Windows Security.
3. Click the Windows Security app from the search results.
4. Click on Virus & threat protection.

Method 3: Using System Tray

1. Click the up arrow in the system tray (bottom-right corner of your screen).
2. Click the shield icon to open Windows Security.
3. Click on Virus & threat protection.

Types of Scans Available

Microsoft Defender offers three types of scans to meet different security needs:

• Quick Scan: Scans the most common locations where threats are typically found. Takes 5-15 minutes and is recommended for regular checks.
• Full Scan: Scans all files and programs on your hard drive. Takes 1-2 hours or longer depending on your system size and is recommended when you suspect an infection.
• Custom Scan: Allows you to select specific drives, folders, or files to scan. Useful when you want to check particular locations without scanning the entire system.

Running a Quick Scan

A quick scan is the fastest option and checks the most vulnerable areas of your system.

1. Open Windows Security using one of the methods above.
2. Ensure you are on the Virus & threat protection page.
3. Under "Current threats," click Quick scan.
4. Wait for the scan to complete. The progress bar will show scanning status.
5. Review the results when the scan finishes. If threats are found, follow the prompts to remove or quarantine them.

Running a Full Scan

A full scan provides comprehensive protection by checking every file on your computer.

1. Open Windows Security and navigate to Virus & threat protection.
2. Under "Current threats," click Scan options.
3. Select the radio button next to Full scan.
4. Click Scan now.
5. The scan will run in the background. You can continue working, though system performance may be slower.
6. You will receive a notification when the scan completes. Click the notification to view results.

Running a Custom Scan

Use a custom scan when you want to check specific locations on your computer.

1. Open Windows Security and go to Virus & threat protection.
2. Click Scan options under "Current threats."
3. Select the radio button next to Custom scan.
4. Click Scan now.
5. In the file browser window that appears, navigate to the folder or drive you want to scan.
6. Select the location and click Select Folder.
7. The scan will begin on your selected location.
8. Review the results when the scan completes.

Running an Offline Scan

Microsoft Defender Offline scan is designed to detect and remove difficult-to-find malware that loads before Windows starts.

1. Open Windows Security and go to Virus & threat protection.
2. Click Scan options.
3. Select the radio button next to Microsoft Defender Offline scan.
4. Click Scan now.
5. Click Scan in the confirmation dialog box.
6. Your computer will restart and perform the scan before Windows loads. This process takes approximately 15 minutes.
7. After the scan completes, your computer will restart normally and display the scan results.

Viewing Scan History and Threat Details

You can review previous scans and any detected threats at any time.

1. Open Windows Security and select Virus & threat protection.
2. Under "Current threats," click Protection history.
3. Review the list of detected threats, blocked files, and completed scans.
4. Click on any item to see more details about that threat or action.

Managing Detected Threats

When Microsoft Defender finds a threat, it will automatically take action based on the threat level:

• Severe or High threats: Automatically removed or quarantined.
• Medium or Low threats: You may be prompted to choose an action.

To manually manage quarantined items:

1. Go to Virus & threat protection in Windows Security.
2. Click Protection history.
3. Find quarantined items and click on them for options.
4. Select Remove to permanently delete the threat, or Restore if you believe it was incorrectly identified (use caution).

Scheduling Automatic Scans

Microsoft Defender automatically performs regular quick scans when your computer is idle. To customize scan schedules:

1. Press Windows key + R to open the Run dialog.
2. Type taskschd.msc and press Enter.
3. In Task Scheduler, navigate to Task Scheduler Library > Microsoft > Windows > Windows Defender.
4. Double-click on Windows Defender Scheduled Scan.
5. Click the Triggers tab to modify the schedule.
6. Click Edit to change the existing schedule or New to add another schedule.
7. Set your preferred schedule and click OK.

Troubleshooting Common Issues

Scan Won't Start

• Ensure Windows is up to date by going to Settings > Windows Update.
• Verify that Microsoft Defender is enabled and not disabled by group policy or another antivirus program.
• Restart your computer and try again.

Scan Taking Too Long

• Full scans can take several hours on systems with large amounts of data. This is normal.
• Close unnecessary programs to free up system resources.
• If you need to stop a scan, you can click Cancel in the Windows Security window.

False Positives

If Microsoft Defender flags a file you trust as a threat:

1. Review the threat details carefully before taking action.
2. If you're certain the file is safe, you can restore it from quarantine.
3. Add the file to exclusions by going to Virus & threat protection > Manage settings, then scrolling to "Exclusions" and clicking Add or remove exclusions.

Need Additional Support?

This guide aims to provide useful information, but as technology changes, interfaces or steps might vary. Please use the Comment button to let us know if anything differs from your experience. Your feedback helps us keep this information accurate. Thank you!