Malware can affect Windows computers in different ways, including slowing down system performance, displaying unwanted advertisements, changing browser settings, and interfering with normal computer operations. Some malicious programs may also attempt to collect personal information or install unwanted applications.
If your Windows computer is behaving unusually, it is important to investigate the problem and take appropriate security measures.
Fortunately, Windows includes built-in security tools that can help users identify and remove many common malware threats.
In this guide, we explain how to remove malware from Windows, how to scan your computer using Microsoft Defender, and how to improve your computer’s security to reduce the risk of future infections.
What Is Malware?
Malware is short for malicious software. It refers to programs designed to perform unwanted activities on a computer or access information without the user’s permission.
There are several types of malware that can affect Windows computers.
Some common examples include:
- Computer viruses: Programs that can attach themselves to other files and spread when those files are executed.
- Trojans: Applications disguised as legitimate software to encourage users to install them.
- Spyware: Software designed to collect information about a user’s activities.
- Adware: Programs that display unwanted advertisements.
- Ransomware: Malware that can restrict access to files by encrypting them.
- Browser hijackers: Programs that modify browser settings, search preferences, or homepage configurations.
Understanding these threats can help users recognise unusual computer behaviour and take appropriate action.
Common Signs of Malware on Windows Computers
Malware does not always produce obvious symptoms. However, some unusual computer activities may indicate a possible security problem.
Here are some signs worth investigating:
- Your computer becomes unusually slow.
- Unexpected advertisements appear while browsing.
- Your browser redirects to unfamiliar websites.
- Unknown applications appear in your installed programs.
- Your homepage or default search engine changes unexpectedly.
- Windows Security displays a threat notification.
- Your computer frequently freezes or crashes.
- Unfamiliar browser extensions appear.
- Your computer experiences unexplained changes in performance.
These symptoms can also result from software conflicts, outdated applications, or hardware problems. Therefore, running a security scan is a sensible first step.
How to Remove Malware from Windows
If you suspect that your computer has malware, follow these steps to check your system and remove potentially harmful software.
Step 1: Disconnect Your Computer from the Internet if Necessary
If you suspect an active malware infection, temporarily disconnect your computer from Wi-Fi or unplug its Ethernet cable.
This may help limit communication between certain types of malware and external servers.
Avoid accessing banking services or entering sensitive account information on a computer that you suspect may be compromised.
You can reconnect when necessary to download security updates or complete the cleanup process.
Step 2: Open Windows Security
Windows includes a built-in security application called Windows Security.
It provides access to Microsoft Defender Antivirus and other security features.
To open it:
- Click the Start menu.
- Open Settings.
- Select Privacy & security.
- Click Windows Security.
- Select Virus & threat protection.
You can also type Windows Security into the Start menu search box.
Step 3: Update Microsoft Defender Antivirus
Before scanning your computer, check whether your antivirus security intelligence is up to date.
Follow these instructions:
- Open Windows Security.
- Select Virus & threat protection.
- Find Virus & threat protection updates.
- Click Protection updates.
- Select Check for updates.
Updated security intelligence helps Microsoft Defender recognise newer threats.
Step 4: Perform a Full System Scan
A full scan checks files and running programs across your computer for potential security threats.
To perform a full scan:
- Open Windows Security.
- Select Virus & threat protection.
- Click Scan options.
- Choose Full scan.
- Click Scan now.
Allow the process to finish.
The scanning time depends on your computer’s storage capacity, the number of files, and overall system performance.
If Microsoft Defender identifies a threat, review the results and follow the recommended instructions to quarantine or remove it.
Step 5: Use Microsoft Defender Offline Scan
Some malware may be difficult to remove while Windows is running.
Microsoft Defender Offline provides another scanning option by restarting your computer and checking for threats outside the normal Windows environment.
To use it:
- Open Windows Security.
- Select Virus & threat protection.
- Click Scan options.
- Select Microsoft Defender Offline scan.
- Click Scan now.
Save your work before starting because your computer will restart.
After the scan, Windows should restart automatically. You can review the scan results under Protection history.
Step 6: Remove Unwanted Applications
Some potentially unwanted programs may remain installed on your computer.
Review your installed applications and remove programs that you have identified as unnecessary or untrusted.
On Windows 11:
- Open Settings.
- Select Apps.
- Click Installed apps.
- Review the applications listed.
- Research unfamiliar programs before uninstalling them.
- Remove applications you have confirmed are unwanted.
On Windows 10, navigate to Settings, Apps, and Apps & features.
Be careful not to remove essential Windows components, system drivers, or applications you do not recognise without checking their purpose.
Step 7: Check Your Browser Extensions
Unwanted browser extensions can sometimes change search settings, display advertisements, or redirect users to unfamiliar websites.
For Google Chrome:
- Open Chrome.
- Click the three-dot menu.
- Select Extensions.
- Choose Manage Extensions.
- Review the installed extensions.
- Remove extensions you do not recognise or trust.
For Microsoft Edge, open the browser menu and select Extensions.
You should also review website notification permissions and remove permission from unfamiliar websites.
Step 8: Review Startup Applications
Some unwanted programs may configure themselves to launch automatically when Windows starts.
To review startup applications:
- Press Ctrl + Shift + Esc.
- Open Task Manager.
- Select Startup apps.
- Review the applications listed.
- Disable unfamiliar or unnecessary programs after verifying their purpose.
Disabling a startup application does not necessarily remove malware. It is an additional step that may help identify unwanted background activity.
Step 9: Install Available Windows Updates
Keeping Windows updated helps protect your computer against known security vulnerabilities.
To check for updates:
- Open Settings.
- Select Windows Update.
- Click Check for updates.
- Install available updates.
- Restart your computer if required.
For continued protection, use a Windows version that receives security updates. Standard Windows 10 support ended on October 14, 2025, although eligible extended security update options may be available.
Step 10: Change Important Account Passwords
If you suspect that malware may have accessed your personal information, consider changing passwords for important accounts.
Use a separate, trusted device to make these changes.
Prioritise your:
- Email accounts.
- Banking accounts.
- Social media accounts.
- Online shopping accounts.
- Cloud storage accounts.
Use unique passwords and enable two-factor authentication wherever possible.
What Should You Do If Malware Keeps Returning?
If malware continues to appear after you have completed a cleanup, further investigation may be necessary.
Possible reasons include:
- Another unwanted application remains installed.
- A suspicious browser extension has not been removed.
- A malicious program is reinstalling unwanted components.
- An infected file has been restored from a backup.
- The computer has a persistent security problem.
Consider running another full scan and using Microsoft Defender Offline.
If the problem continues, seek help from a qualified computer technician.
A Windows reset or clean installation may be necessary in severe cases. Before proceeding, back up important personal documents carefully and avoid transferring suspicious applications or executable files.
How to Protect Your Windows Computer from Future Malware
Removing malware is only one part of maintaining computer security. Developing safer browsing and downloading habits can also reduce the risk of future infections.
Here are some practical precautions.
1. Keep Your Operating System Updated
Install available Windows security updates and keep supported applications updated.
2. Use Reliable Antivirus Protection
Keep Microsoft Defender Antivirus or another reputable antivirus solution active and updated.
Avoid installing unfamiliar security programs advertised through unexpected pop-ups.
3. Download Applications from Official Sources
Whenever possible, download software from official developer websites or trusted application stores.
Check the publisher and installation instructions before installing unfamiliar programs.
4. Avoid Suspicious Email Attachments
Be careful with unexpected email attachments and links, particularly messages requesting urgent action or personal information.
Verify the sender before opening unfamiliar files.
5. Use Strong Passwords
Create unique passwords for important accounts and enable two-factor authentication.
A reputable password manager can help organise your login details.
6. Back Up Important Files
Regularly back up important documents, photographs, and other personal files.
An external storage device or reputable cloud backup service can help protect important information.
7. Review Your Browser Settings
Periodically check installed extensions, notification permissions, homepage settings, and default search engines.
Remove anything you have identified as unwanted.
Frequently Asked Questions
1. How do I remove malware from Windows without installing additional software?
You can use Microsoft Defender Antivirus, which is included with Windows Security. Open Virus & threat protection, update your security intelligence, and perform a full scan.
2. Can Microsoft Defender remove malware?
Yes. Microsoft Defender Antivirus can detect, quarantine, and remove many common malware threats. Its effectiveness depends on the threat, its configuration, and whether its security intelligence is up to date.
3. How do I scan Windows 11 for malware?
Open Settings, select Privacy & security, then Windows Security. Choose Virus & threat protection, select Scan options, and run a Full scan.
4. What is Microsoft Defender Offline?
Microsoft Defender Offline is a security scanning feature that restarts your computer and checks for certain threats outside the normal Windows environment.
5. Can malware slow down my computer?
Yes. Some malicious programs consume system resources, run unwanted background processes, or interfere with normal computer operations. However, slow performance can also have other causes.
6. Will resetting Windows remove malware?
A Windows reset or clean installation can remove many software-based infections, but it is not a guarantee against every possible threat. Make sure important files are backed up carefully and restore only trusted data.
7. Can malware steal personal information?
Some types of malware are designed to collect personal information, monitor activities, or access account credentials. If you suspect information has been exposed, change important passwords using a trusted device.
8. How often should I scan my Windows computer?
Keep real-time antivirus protection enabled and allow automatic security updates. You can also run a manual full scan when you notice unusual behaviour or have other reasons to suspect a security issue.
Final Verdict
Malware can affect the performance, security, and normal operation of Windows computers. Fortunately, Windows provides useful built-in security features that can help users identify and remove many common threats.
If you suspect that your computer has malware, begin with Microsoft Defender Antivirus and perform a full system scan. For persistent problems, consider using Microsoft Defender Offline and reviewing recently installed applications and browser extensions.
Most importantly, keep Windows updated, download software from trusted sources, use strong passwords, and back up important files regularly.
By following these practical security measures, you can improve your computer’s protection and reduce the likelihood of future malware infections.
