If you need help with Windows Defender customer support, the best place to start is the built-in Microsoft security tools and official Microsoft Support resources. Microsoft Defender (formerly Windows Defender) is integrated into Windows, so there is no separate customer support department dedicated only to Defender. You can troubleshoot security issues using the Windows Security app, run built-in diagnostics, check for Windows updates, and contact Microsoft Support if you need additional assistance with malware detection, scans, updates, or Defender settings.
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Main Steps
Follow these steps to get help with Microsoft Defender.
1. Open Windows Security
Windows Defender is managed through the Windows Security application.
1. Click the Start menu.
2. Type Windows Security.
3. Open the application.
4. Review the security dashboard.
You can quickly see whether your device has any security alerts or recommended actions.
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2. Check Virus & Threat Protection
Select Virus & Threat Protection.
From here you can:
• Run a Quick Scan
• Perform a Full Scan
• Start a Microsoft Defender Offline Scan
• View Protection History
• Check security recommendations
If Windows Defender detects malware, follow the recommended removal steps.
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3. Install Windows Updates
Many Defender issues are resolved by installing the latest Windows updates.
1. Open Settings.
2. Select Windows Update.
3. Click Check for updates.
4. Install all available updates.
5. Restart your computer.
Security intelligence updates are delivered through Windows Update.
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4. Update Microsoft Defender Security Intelligence
Updated security definitions help Defender recognize the latest threats.
Within Windows Security:
• Open Virus & Threat Protection
• Select Protection Updates
• Check for updates
Keeping security intelligence current improves malware detection.
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5. Run a Full System Scan
If you suspect malware:
1. Open Windows Security.
2. Select Virus & Threat Protection.
3. Click Scan options.
4. Choose Full Scan.
5. Start the scan.
Large drives may require considerable time to complete.
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6. Use Microsoft Defender Offline Scan
If malware prevents Windows from operating normally:
1. Open Scan Options.
2. Select Microsoft Defender Offline Scan.
3. Restart your PC.
The scan runs before Windows fully loads, helping remove difficult threats.
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7. Contact Microsoft Support
If Defender continues showing errors or fails to operate correctly, use Microsoft's official support channels available through the Windows Get Help app or Microsoft Support website.
Before requesting assistance, prepare:
• Windows version
• Error messages
• Device model
• Recent updates
• Troubleshooting already completed
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Platform-Specific Instructions
Windows 11
Windows Defender is built into Windows 11 as Microsoft Defender Antivirus.
You can:
• Run malware scans
• Update virus definitions
• Enable Real-Time Protection
• Configure Firewall
• Review Device Security
• Monitor account protection
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Windows 10
Windows Defender functions similarly in Windows 10.
Use Windows Security to:
• Run scans
• Manage ransomware protection
• Configure firewall settings
• View protection history
• Check update status
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Mac
Microsoft Defender is available separately for supported Microsoft Defender business and Microsoft 365 environments.
Consumer Windows Defender features are not included with macOS.
Mac users should install the appropriate Microsoft Defender application if provided through their organization.
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Android
Microsoft Defender is available for certain Microsoft subscriptions.
Depending on your subscription, Android users may receive:
• Malware protection
• Web protection
• Privacy monitoring
• Security alerts
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iPhone and iPad
Microsoft Defender is available for eligible Microsoft accounts and subscriptions.
Features may include:
• Web protection
• Identity monitoring
• Security notifications
• Device protection guidance
Available features depend on your subscription plan.
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Important Information
Windows Defender Is Built Into Windows
Most Windows 10 and Windows 11 devices include Microsoft Defender automatically.
You do not need to purchase or activate it separately.
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Microsoft Account
A Microsoft account is not required simply to use Microsoft Defender Antivirus.
However, signing in may be necessary for:
• Microsoft Defender app features
• Family Safety
• Microsoft 365 security services
• Cross-device protection
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Keep Windows Updated
Defender depends on Windows Update for:
• Security intelligence updates
• Bug fixes
• Engine improvements
• Feature enhancements
Delaying updates can reduce protection.
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Third-Party Antivirus
Installing another antivirus program may disable Microsoft Defender Antivirus automatically.
This behavior prevents software conflicts.
If you remove the third-party antivirus, Defender usually reactivates after a restart.
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Internet Connection
Certain Defender features require internet access, including:
• Cloud-delivered protection
• Definition updates
• Reputation-based protection
• SmartScreen services
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Administrator Permissions
Some Defender settings require administrator rights.
Standard users may not be able to:
• Change security policies
• Disable protections
• Modify firewall rules
• Manage exclusions
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Troubleshooting
Problem
Windows Defender will not open.
Cause
Corrupted Windows files, disabled services, or conflicting security software.
Solution
Restart the computer, install Windows updates, uninstall incompatible antivirus software, and run the System File Checker if necessary.
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Problem
Virus definitions are not updating.
Cause
Internet connectivity issues, Windows Update problems, or disabled update services.
Solution
Verify your internet connection, restart Windows Update services, and manually check for updates through Windows Security.
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Problem
Real-Time Protection keeps turning off.
Cause
Another antivirus application may be controlling system protection.
Solution
Remove conflicting antivirus software if you want Microsoft Defender to provide primary protection, then restart Windows.
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Problem
A scan never finishes.
Cause
Large files, damaged storage, or software conflicts.
Solution
Restart the PC, close unnecessary applications, update Windows, and try the scan again.
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Problem
Windows Defender reports repeated threats.
Cause
Malware may be reinstalling itself or hiding in startup programs.
Solution
Run Microsoft Defender Offline Scan, remove suspicious applications, review startup programs, and update Windows before scanning again.
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Problem
Firewall settings cannot be changed.
Cause
Administrator policies or organizational management.
Solution
Sign in using an administrator account or contact your organization's IT administrator if the computer is managed.
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Special Cases
New Windows Computer
A new Windows PC usually includes Microsoft Defender automatically.
After setup:
• Install Windows updates.
• Verify Real-Time Protection is enabled.
• Run an initial scan.
• Update security intelligence.
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Business Computers
Organizations may manage Microsoft Defender through Microsoft Intune, Microsoft Defender for Endpoint, or Group Policy.
Employees may need to contact their IT department for changes to security settings.
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Windows Defender Disabled After Installing Antivirus
When another antivirus product is installed, Microsoft Defender often switches to passive mode or disables antivirus protection automatically.
Removing the third-party antivirus generally restores Defender after restarting the device.
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Device After Windows Reset
If Windows is reset or reinstalled, Microsoft Defender is automatically restored as part of the operating system.
After setup, install all available Windows updates before relying on the device for regular use.
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Low Storage Devices
Insufficient storage may prevent updates and scans from completing successfully.
Delete unnecessary files or use Storage Sense to free space before updating Defender.
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Multiple Windows Devices
If you use multiple Windows devices with the same Microsoft account and eligible Microsoft services, you may be able to monitor security information across supported devices.
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Frequently Asked Questions
Is Windows Defender the same as Microsoft Defender?
Yes. Windows Defender Antivirus has been renamed Microsoft Defender Antivirus. It remains the built-in antivirus solution included with Windows 10 and Windows 11.
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Is there a Windows Defender customer support phone number?
Microsoft Defender does not have a separate customer support department dedicated only to Defender. If you need assistance, use Microsoft's official support resources through the Get Help app or Microsoft Support website.
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Is Microsoft Defender free?
Yes. Microsoft Defender Antivirus is included with supported versions of Windows at no additional cost. Some advanced Microsoft Defender features are available only through eligible Microsoft subscriptions.
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Can Microsoft Defender remove malware?
Yes. Microsoft Defender can detect, quarantine, and remove many types of viruses, spyware, ransomware, trojans, and other malicious software when its security intelligence is kept up to date.
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Why is Microsoft Defender turned off?
Microsoft Defender may be disabled automatically if another antivirus program is installed. In managed business environments, administrators may also control Defender through organizational policies.
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How often should I run a scan?
Real-Time Protection continuously monitors your computer. Running a Quick Scan weekly and a Full Scan periodically provides additional assurance, especially after downloading files from unfamiliar sources.
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Does Microsoft Defender protect against ransomware?
Yes. Microsoft Defender includes ransomware protection features, including Controlled Folder Access on supported Windows devices. Keeping Windows updated improves protection against newly discovered threats.
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Can I use Microsoft Defender without a Microsoft account?
Yes. Basic antivirus protection works without signing in. However, certain Microsoft security services and subscription-based features may require a Microsoft account.
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Why can't I update Microsoft Defender?
Update problems are often caused by Windows Update issues, internet connectivity problems, insufficient storage, or temporary service interruptions. Installing pending Windows updates usually resolves most update-related errors.
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When should I contact Microsoft Support?
Contact Microsoft Support if Microsoft Defender will not start, repeatedly crashes, cannot update, reports persistent errors, or continues detecting threats that cannot be removed after completing recommended troubleshooting steps.