How to Scan Your Windows PC for Viruses and Malware for Free Using Built-In Tools

How to Scan Your Computer for Viruses and Malware Using Free Windows Tools​

Is your computer running unusually slow? Are you seeing strange pop-ups or experiencing unexplained crashes? Your system might be infected with viruses or malware, but the good news is you don't have to spend a dime on expensive security software to find and remove these threats. Microsoft's Windows operating system includes a powerful security suite — Windows Security (formerly known as Windows Defender) — built right in to protect your PC. This comprehensive guide will walk you through everything from basic manual scanning to using more advanced tools available for free on Windows 10 and 11.

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Unlocking the Power of Windows Security: Your Free Protector​

Windows Security is Microsoft's integrated defense system designed to protect your PC against malware, viruses, spyware, ransomware, and other malicious software. It has evolved significantly from its early days as Windows Defender, now providing real-time protection, cloud-powered threat analysis, and deep integration with the operating system. Because it’s built in, it runs with minimal system impact while updating virus definitions frequently — often multiple times a day — to stay ahead of emerging threats.
Key components of Windows Security include:

• Virus & Threat Protection: The core antivirus scanner.
• Firewall & Network Protection: Guards against network intrusions.
• App & Browser Control: Protects you when browsing and downloading.
• Device Security: Hardware-level security like encryption.
• Account Protection: Safeguards login credentials and sign-in options.

All these layers work together to create a strong security shield without the need for complicated settings or additional purchases.

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How to Perform a Quick Scan to Detect Threats Fast​

When your computer exhibits suspicious behavior, a Quick Scan is the fastest way to check the most likely hiding places for malware, such as system folders where threats commonly lodge.
Steps to perform a Quick Scan:

• Open the Start Menu and search for Windows Security.
• Launch the Windows Security app.
• Click on Virus & Threat Protection.
• Locate and click the Quick scan button under the Current threats section.

This scan usually completes within minutes and runs in the background so you can continue using your computer. Once finished, Windows Security will notify you of any detected threats and assist you with options to quarantine or remove them.

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Diving Deeper: Full and Custom Scans for Thorough Protection​

While quick scans are great for everyday checks, sometimes you need to be more exhaustive.

• Full Scan: This option inspects every file and running process on your entire system. It is particularly useful if you’ve experienced prolonged symptoms of infection or haven’t scanned in a while.
• Custom Scan: Allows you to pick specific folders or external drives to scan, perfect if you want to check a new USB stick or a suspicious download folder.
• Microsoft Defender Offline Scan: This boots your PC into a special environment before Windows loads and hunts for rootkits or deeply embedded malware.

To access these:

• In Windows Security, go to Virus & Threat Protection.
• Scroll down and click Scan options.
• Choose Full scan, Custom scan, or Microsoft Defender Offline scan, depending on your need.
• Click Scan now.

Keep in mind, full scans can take an hour or more, so it’s best to run them when you don’t need immediate access to your PC. The Offline scan requires a reboot but provides powerful remediation for stubborn infections.

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Managing Threats: Quarantine, Removal, and False Positives​

When Windows Security detects malware, it will typically quarantine suspicious files automatically, preventing them from causing harm but not deleting them immediately. You can review these quarantined items and decide to delete or restore if you believe a file was flagged incorrectly.
How to review detected threats:

• Open Windows Security.
• Navigate to Virus & Threat Protection.
• Scroll to Protection history to see all recent threat detections and actions taken.

Sometimes legitimate software can be mistakenly flagged as malicious — a false positive. In such cases, you can allow the file or program on your device, but only do this if you are absolutely certain it’s safe.

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Keeping Windows Security Up to Date for Maximum Efficacy​

Virus definitions are the database entries that tell Windows Security what malware looks like. Keeping this updated is critical.
To manually update virus definitions:

• Open Windows Security.
• Go to Virus & Threat Protection.
• Scroll down to Virus & threat protection updates.
• Click Check for updates.

Windows also automatically updates these definitions via Windows Update, but manually checking ensures you get the very latest protection immediately.

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Advanced Scanning Methods for Power Users​

If you’re comfortable with command-line tools, Windows provides multiple ways to invoke scans via:

• Command Prompt:
• Run Command Prompt as administrator.
• Use commands such as:
  "%ProgramFiles%\Windows Defender\MpCmdRun.exe" -Scan -ScanType 1 for a quick scan.
  "%ProgramFiles%\Windows Defender\MpCmdRun.exe" -Scan -ScanType 2 for a full scan.
• PowerShell:
• Run PowerShell as administrator.
• Use the command:
  Start-MpScan -ScanType FullScan or for scanning specific paths,
  Start-MpScan -ScanType CustomScan -ScanPath "C:\Path\To\Folder".

These methods offer more control, allowing scripting and automation suited to IT professionals or advanced users who want fine-tuned scan management.

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Scheduling Automatic Scans to Maintain Ongoing Security​

Windows Security runs regular background scans, but you can also schedule specific scan tasks using the Windows Task Scheduler to run quick or full scans on a set timetable.
How to schedule scans:

• Open Task Scheduler (search in Start menu).
• Select Create Basic Task.
• Name your task (e.g., “Weekly Full Scan”).
• Choose a trigger (daily, weekly, etc.).
• Set the action to start a program.
• Program/script path is:
  "%ProgramFiles%\Windows Defender\MpCmdRun.exe"
• Add arguments for the scan type, e.g., -Scan -ScanType 2 for a full scan.

This ensures you never forget regular deep clean checks, keeping your system secure without hands-on intervention.

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Microsoft Defender Offline: The Heavy-Hitter Against Persistent Threats​

Some malware hides so deeply that it evades normal scans. Microsoft Defender Offline specializes in these tough cases by running a scan before Windows boots, preventing malware from hiding behind active defenses.
Running Microsoft Defender Offline:

• Save all work and close apps.
• Open Windows Security.
• Go to Virus & Threat Protection → Scan options.
• Select Microsoft Defender Offline scan and start it.
• Your PC will restart and perform the scan outside of normal Windows operations.
• After completion, check the Protection history for results.

This is essential if you suspect rootkits or persistent infections.

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Tips for Optimal Protection and Malware Prevention​

• Always enable real-time protection in Windows Security settings to catch threats as they arise.
• Uninstall any suspicious or unknown software promptly.
• Keep Windows and software updated at all times to patch security vulnerabilities.
• Practice safe browsing and downloading habits — only download from trusted sources.
• Perform regular backups of important data to an external drive or cloud service.
• Consider complementary third-party antivirus software if handling sensitive data or requiring extra features.

By maintaining a proactive security approach combining Windows Security’s free capabilities with practical habits, you create a robust barrier against malware.

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Conclusion​

You don’t need expensive third-party antivirus software to keep your computer safe. Windows Security, Microsoft’s free and integrated protection suite, offers comprehensive features to detect, remove, and prevent malware infections effectively. From quick scans for routine checks to deep full and offline scans for stubborn infections, it’s equipped to safeguard a broad range of threats. With real-time protection, frequent updates, and easy-to-use interfaces, this built-in tool is a powerful ally for both casual users and professionals looking to maintain system integrity without additional cost. By following this guide, you can confidently scan your Windows 10 or 11 PC for viruses and malware anytime for free and keep your computer running smoothly and securely.

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Feel free to refer to the various in-depth details and step-by-step tutorials embedded in Windows itself or reach out for assistance with advanced tools and troubleshooting for persistent threats. Your PC’s health and peace of mind are well within reach — at no extra cost.

Stay safe, scan regularly, and keep your system defended!​

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Source: 9meters Steps to Scan Your Computer for Free and Check for Viruses and Malware - 9meters