In some cases Microsoft security software might not be able to completely remove malware from your PC. Usually this is because the malware is embedded in a system file that cannot be cleaned or it’s in a .ZIP file that’s too large to clean.
When this happens, you might see a message from your security software telling you that the malware can’t be removed.
A special case of re-infection: Exploits
Exploits are threats that try to use vulnerabilities in common software to infect your PC. If your security software is warning you about an exploit that isn’t being cleaned, it might be because you are using vulnerable software.
What you need to do
There are three steps you can take to try to resolve this issue:
Update your security software and run a full scan
The first thing you should do is update your antivirus or antimalware software definitions. You can get the latest definitions from our updates page.
Once you have updated, run a full scan.
Read the Microsoft Malware Protection Center encyclopedia
Most of the time Microsoft security software will remove any malware that it detects. Sometimes you may need to take some extra steps to completely recover your computer or avoid getting reinfected.
You can find this extra information by searching our encyclopedia.
To find relevant encyclopedia entry you can either:
Click on the Get more information about this item online link that pops up in your Microsoft security software when the malware is detected
Visit the encyclopedia and search with the name of the malware that is being detected
Restore your PC from backup
If you are still getting alerts about a malware infection after following the steps above, you may need to restore your PC from backup. Once you restore your systems you should reinstall your security software.
To restore your PC from backup:
Restore or reinstall Windows
Perform a clean install of your operating system. Back up any files and settings you want to keep so that you can restore them later. You'll need to reinstall your programs, so make sure you have the installation discs, product keys, or setup files.
These articles have more information:
Reinstall security software
If you’re running Windows 8, your PC comes with Windows Defender built in. Windows Defender helps guard your PC against viruses, spyware, and other malicious software in real time
If you’re running Windows 7 or Windows Vista, install security software such as Microsoft Security Essentials or other security software that provides a complete, real-time antimalware solution
Keep your antimalware software up-to-date by making sure you have the latest definitions
Microsoft security software will usually “quarantine” any threats it finds. This gives you the choice to remove it or not. Quarantined threats will look like this:
To remove quarantined threats:
Check the box next to the threat you want to remove
Click Remove all
If you are asked to confirm this action, click Yes and the threat will be removed.