How to Scan Your Device for Malware on Windows: A Practical Guide in 2026

Your Windows computer is acting strange. Programs crash without warning. Pop-ups appear from nowhere. Your system runs slower than usual.

These are signs of malware infection.

The quickest way to scan your Windows device for malware is using Windows Security (built into Windows 10 and 11), running a full scan that checks every file and program on your computer. This takes 30-60 minutes but catches most threats without installing anything extra.

This guide shows you exactly how to scan for malware, remove threats, and protect your device going forward.

What Is Malware and Why Should You Care

Malware is malicious software designed to harm your computer or steal your information.

Common types include:

• Viruses that spread by attaching to files
• Trojans that disguise themselves as legitimate programs
• Spyware that tracks your activity and steals passwords
• Ransomware that locks your files and demands payment
• Adware that floods you with unwanted advertisements

The average cost of a malware attack on individuals ranges from $200 to $5,000 when you factor in data loss, identity theft, and system repairs.

Signs Your Windows Device Has Malware

Watch for these warning signals:

Performance issues: Computer runs extremely slow, freezes frequently, or crashes without reason.

Strange behavior: Programs open or close by themselves. Your browser homepage changed without your permission. New toolbars appeared.

Security alerts: Antivirus software disabled itself. Windows Defender won’t turn on. Firewall settings changed.

Network activity: Internet usage spikes when you’re not doing anything. Your connection feels sluggish.

File problems: Files disappear, get encrypted, or won’t open. New files appear that you didn’t create.

If you notice multiple symptoms, scan immediately.

How to Scan for Malware Using Windows Security

Windows Security comes free with Windows 10 and 11. It’s your first line of defense.

Running a Quick Scan

A quick scan checks the most common infection points in under 5 minutes.

1. Click the Start button
2. Type “Windows Security” and press Enter
3. Select “Virus & threat protection”
4. Click “Quick scan”
5. Wait for the scan to complete
6. Review any threats found

Quick scans work well for regular checks but miss hidden malware.

Running a Full Scan for Complete Protection

Full scans examine every file, folder, and program. They take longer but find more threats.

1. Open Windows Security
2. Go to “Virus & threat protection”
3. Click “Scan options”
4. Select “Full scan”
5. Click “Scan now”
6. Let it run (this takes 30-90 minutes)
7. Review the results when finished

Run full scans at least once per month, preferably when you won’t need your computer for other tasks.

Using Microsoft Defender Offline Scan

Some malware hides so well that regular scans can’t detect it. The offline scan restarts your computer and scans before Windows loads.

1. Open Windows Security
2. Select “Virus & threat protection”
3. Click “Scan options”
4. Choose “Microsoft Defender Offline scan”
5. Click “Scan now”
6. Save your work (your computer will restart)
7. Confirm you want to proceed

Your computer restarts, runs the scan (takes 15 minutes), then boots normally.

Use this when you suspect deep infections that regular scans miss.

Scanning with Third-Party Antivirus Software

Windows Security handles most threats, but sometimes you need a second opinion.

Best Free Scanning Tools

Malwarebytes Free excels at finding threats that other scanners miss. Download from malwarebytes.com, install it, and run a “Threat Scan.”

Bitdefender Free offers strong detection rates without slowing your system. It works alongside Windows Security for extra protection.

Kaspersky Security Cloud Free provides excellent malware detection and includes privacy tools.

How to Use Multiple Scanners Safely

Running two real-time antivirus programs causes conflicts. Here’s the right approach:

1. Keep Windows Security as your main protection (always running)
2. Install a second scanner like Malwarebytes
3. Disable real-time protection in the second scanner
4. Run manual scans with the second tool weekly
5. Let Windows Security handle continuous protection

This gives you multiple detection engines without system conflicts.

Advanced Scanning Techniques

Safe Mode Scanning

Malware sometimes prevents scanners from running properly. Safe Mode loads Windows with minimal programs, making it harder for malware to interfere.

1. Click Start, then Power
2. Hold Shift and click Restart
3. Select “Troubleshoot” then “Advanced options”
4. Choose “Startup Settings” and click Restart
5. Press 4 or F4 for Safe Mode
6. Open your antivirus and run a full scan
7. Restart normally when done

Use Safe Mode when scans won’t complete or when malware keeps reappearing.

Bootable Antivirus Scanners

The most stubborn malware resists all normal removal methods. Bootable scanners run from a USB drive before Windows starts.

Creating a rescue disk:

1. Download a rescue disk tool (Kaspersky, Bitdefender, or AVG offer free versions)
2. Insert a USB drive (8GB minimum)
3. Run the rescue disk creator
4. Follow the prompts to create the bootable drive
5. Restart your computer
6. Boot from the USB (press F12, F2, or Del during startup)
7. Run the scan from the rescue environment

This works when Windows won’t start or when infections are severe.

What to Do After Finding Malware

Removing Detected Threats

Most scanners quarantine or delete threats automatically. If you need to take action:

Quarantine first: This isolates the threat without deleting it. Choose this if you’re uncertain.

Delete permanently: Use this for confirmed malware. Windows Security and other tools mark clearly malicious files.

Restore false positives: Sometimes legitimate files get flagged. Research the file name online before restoring.

Checking for Remaining Problems

After removal, verify your system is clean:

1. Run a second full scan with a different tool
2. Check Task Manager (Ctrl + Shift + Esc) for suspicious processes
3. Review startup programs (Settings > Apps > Startup)
4. Check browser extensions for unfamiliar items
5. Scan again in Safe Mode if problems persist

Changing Your Passwords

Malware often steals login credentials. After cleaning your system:

1. Change passwords for banking and financial accounts first
2. Update email account passwords
3. Change social media and shopping site passwords
4. Enable two-factor authentication where available
5. Use different passwords for each account

According to the Cybersecurity & Infrastructure Security Agency, stolen credentials account for over 80% of data breaches.

Preventing Future Malware Infections

Keep Windows and Software Updated

Updates patch security holes that malware exploits.

Enable automatic updates:

1. Open Settings
2. Go to “Update & Security”
3. Select “Windows Update“
4. Click “Advanced options”
5. Enable “Receive updates for other Microsoft products”
6. Turn on automatic updates for installed programs

Check for updates weekly even with automatic updates enabled.

Practice Safe Browsing Habits

Most infections come from your online behavior:

Don’t click suspicious links in emails, even from people you know. Verify unexpected messages by calling the sender.

Only download from official sources. Get software directly from company websites or the Microsoft Store.

Avoid pirated content. Cracked software and illegal downloads commonly contain malware.

Watch for warning signs. If a website looks unprofessional or makes unrealistic promises, leave immediately.

Use strong passwords. Combine letters, numbers, and symbols. Make them at least 12 characters long.

Configure Windows Security Properly

1. Open Windows Security
2. Go to “Virus & threat protection”
3. Click “Manage settings”
4. Enable “Real-time protection”
5. Turn on “Cloud-delivered protection”
6. Enable “Automatic sample submission”
7. Activate “Tamper Protection”

These settings strengthen your defenses significantly.

Use a Standard User Account

Administrator accounts can install anything, including malware. Standard accounts add a permission barrier.

Creating a standard account for daily use:

1. Open Settings
2. Select “Accounts” then “Family & other users”
3. Click “Add someone else to this PC”
4. Create the new account
5. Keep it as “Standard user”
6. Use this account for daily tasks
7. Keep your admin account for installations only

This simple change blocks many infections automatically.

Common Scanning Mistakes to Avoid

Skipping full scans: Quick scans miss deeply hidden threats. Run complete scans monthly.

Ignoring scan results: Review what was found. Research unfamiliar detections before dismissing them.

Disabling antivirus temporarily: Even brief gaps in protection create infection opportunities.

Running too many real-time scanners: Multiple active antivirus programs conflict and slow your system.

Forgetting to update definitions: Antivirus software needs current threat information. Update before scanning.

Only scanning when problems appear: Regular scans catch infections before they cause visible damage.

Malware Scanning Schedule

Scan Type	Frequency	When to Use
Quick Scan	Daily	Regular maintenance
Full Scan	Monthly	Comprehensive check
Custom Scan	As needed	Check specific folders
Offline Scan	Quarterly	Deep system cleaning
Safe Mode Scan	When infected	Remove stubborn malware
Second Opinion Scan	Weekly	Catch missed threats

Understanding Scan Results

Threat Severity Levels

Severe: Immediate danger to your data and privacy. Remove instantly.

High: Serious threats that can damage your system. Take action quickly.

Medium: Potentially unwanted programs. Research before deciding.

Low: Minimal risk items. Often safe to ignore or remove based on preference.

False Positives

Not every detection is real malware. False positives happen when legitimate software gets flagged incorrectly.

Before restoring flagged files:

1. Research the file name online
2. Check if it belongs to known software you installed
3. Scan the file again with a different antivirus
4. Upload it to VirusTotal.com for multi-engine analysis
5. Restore only if multiple sources confirm it’s safe

When in doubt, leave it quarantined.

Special Situations

Scanning External Drives

USB drives and external hard drives spread malware between computers.

1. Plug in the external drive
2. Open Windows Security
3. Select “Virus & threat protection”
4. Click “Scan options”
5. Choose “Custom scan”
6. Select the external drive
7. Click “Scan now”

Scan all external storage before opening files from them.

Network-Wide Protection

If one computer on your network has malware, others might too.

Protecting multiple devices:

1. Scan every connected computer
2. Update router firmware
3. Change router password
4. Enable router firewall
5. Create a guest network for visitors
6. Keep shared drives protected

Mobile Device Scanning

Phones and tablets need protection too. Download antivirus apps only from official app stores (Google Play or Apple App Store).

When to Seek Professional Help

Some situations exceed DIY solutions:

• Ransomware encrypted your important files
• Malware keeps returning after multiple removal attempts
• Your computer won’t boot into Windows
• Banking accounts show unauthorized transactions
• You lack technical confidence to proceed safely

Scanning Performance Impact

Scans use system resources. Here’s what to expect:

Quick scans: Minimal impact. You can keep working.

Full scans: Moderate slowdown. Best run during lunch or overnight.

Offline scans: Computer is unusable during the 15-minute scan.

Safe Mode scans: Limited functionality but faster than normal full scans.

Schedule intensive scans when you don’t need your computer for other tasks.

Conclusion

Scanning your Windows device for malware protects your data, privacy, and computer performance.

Start with Windows Security for regular protection. Run quick scans daily and full scans monthly. Use Safe Mode or offline scans for stubborn infections. Add second-opinion scanners like Malwarebytes for extra security.

Prevention matters more than cure. Keep Windows updated, practice safe browsing, use standard user accounts for daily work, and maintain healthy skepticism about downloads and email attachments.

Regular scanning takes minimal effort but saves you from devastating infections. Make it part of your routine, like locking your doors or backing up files.

Your computer stays healthy when you actively protect it.

Frequently Asked Questions

How long does a full malware scan take on Windows?

A full scan typically takes 30 to 90 minutes depending on your hard drive size, number of files, and computer speed. Solid-state drives scan faster than traditional hard drives. Computers with millions of small files take longer than those with fewer large files. You can use your computer during scans, though performance will be slower.

Can Windows Defender detect all types of malware?

Windows Defender (Windows Security) detects most malware types including viruses, trojans, spyware, and ransomware. Independent tests show it catches 95-99% of threats. However, no single antivirus is perfect. Using a second scanner like Malwarebytes for periodic checks improves your detection rate. The combination catches threats that individual scanners miss.

Do I need to pay for antivirus software?

Free antivirus protection is sufficient for most users. Windows Security provides solid baseline protection at no cost. Free versions of Malwarebytes, Bitdefender, and Kaspersky offer excellent scanning. Paid versions add features like VPNs, password managers, and priority support, but these aren’t essential for malware protection. Save your money unless you need specific premium features.

What should I do if a scan finds ransomware?

Disconnect from the internet immediately to prevent the ransomware from spreading or encrypting more files. Do not pay the ransom. Run an offline scan or boot into Safe Mode to remove the infection. Restore encrypted files from backups if available. Contact professional help if critical files are affected and you have no backups. Report the incident to local law enforcement and the FBI’s Internet Crime Complaint Center.

How often should I scan my computer for malware?

Run quick scans daily with Windows Security’s real-time protection active. Perform full scans monthly to check your entire system thoroughly. Add weekly scans with a second-opinion tool like Malwarebytes. Run offline scans quarterly for deep cleaning. Increase frequency if you download files often, visit unfamiliar websites regularly, or notice any suspicious computer behavior.