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Malware help

You can find answers to common questions about malware and virus infections on this page.

If you can't find the answer you're looking for, see these other topics:


You can also visit the Microsoft virus and malware community for more help.

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In some cases, you can recover or restore previous versions of your files. However, the following conditions must be in place:

  • System Restore Point must have been turned on before you were infected with the malware.

  • You must already have detected and removed the malware, and there can be no traces of it on your PC. You can use Windows Defender Offline to fully clean your PC.

  • Your files must be on the same PC you're using to recover them (they can't be on a network or removable drive).

OneDrive for Windows 8.1 also has a means of restoring previous versions of Microsoft documents. Similar to System Restore Point, you can look at the version history and recover files:

  1. Right-click on a document and click Version history.

    Right-click on a document to see a menu which has the option "Version history"
  2. You can then look at previous versions of the document, so you can go back to a version that hasn't been encrypted or changed by malware.

Win32/Keygen is the name we give to programs that claim or try to illegally activate software.

Of the two million PCs every month that are detected as having Win32/Keygen, nearly 50 percent are also infected with malware. Some of the most dangerous malware pretends to be a keygen, such as Win32/Sirefef.

Go to our software piracy information and piracy prevention pages for more information.

Most malware tries to stay hidden, so you may not be able to tell.

Some of the more common symptoms include:

  • Your PC takes a long time to start up.

  • It takes a while to start an app or change between apps.

  • You get a lot of "delivery failed" messages that say you tried to send an email.

  • You notice unusual icons on your desktop or in the notification area on the taskbar.

  • Your web browser doesn’t go to the site you tell it to, has a different start page, opens new windows, or has new toolbars and shortcuts.

  • You get lots of error messages popping up.

Go to our malware infection page to see the most common ways malware can infect your PC.

There is no way to guarantee your PC will be safe from malware. However, there are several ways you can reduce the risk.

The following web pages have some simple tips to help you stay safe:

These articles can help you stay safe from common threats:

Go to our software updates page for links to update vulnerable software.

Malware authors can use known vulnerabilities in common software to attack your PC. Software vendors regularly release updates to fix these vulnerabilities. The best way to stay protected is to keep all your software up-to-date.

Go to our exploits page for more information about vulnerabilities and exploits.

You can find answers to common issues and questions at the Microsoft Community Virus and Malware website.

If you think your PC is infected you can also go to these sites:

If you suspect a file includes malware or potentially unwanted software you can submit it to us for analysis.

Go to our encyclopedia for descriptions about specific threats.