How to remove and avoid computer viruses
A computer virus is malicious software (also known as "malware") that can copy itself and infect other software or files on your computer.
If you suspect your computer has been infected, the Microsoft Windows website provides step-by-step instructions for removing viruses and other malware.
Fortunately, if you update your computer and use free antivirus software such as Microsoft Security Essentials, you can help permanently remove unwanted software and prevent installation in the first place.
Note What you might think is a virus could actually be spyware. Microsoft Security Essentials helps protect against spyware, too.
How do I know if my computer has been infected?
After you open and run an infected program or attachment on your computer, you might not realize that you've introduced a virus until you notice something isn't quite right.
Here are a few indicators that your computer might be infected:
Your computer runs more slowly than normal
Your computer stops responding or freezes often
Your computer crashes and restarts every few minutes
Your computer restarts on its own and then fails to run normally
Applications on your computer don't work correctly
Disks or disk drives are inaccessible
You can't print correctly
You see unusual error messages
You see distorted menus and dialog boxes
These are common signs of infection—but they might also indicate hardware or software problems that have nothing to do with a virus. Unless you run the Microsoft Malicious Software Removal Tool and install industry-standard, up-to-date antivirus software on your computer, there is no way to be certain if your computer is infected with a virus or not.
Tip Beware of messages warning you that you've sent email that contained a virus. This can indicate that the virus has listed your email address as the sender of tainted email. This does not necessarily mean you have a virus. Some viruses have the ability to forge email addresses. In addition, there is a category of malware called rogue security software that works by causing fake virus alerts to pop up on your computer.
How do I install updates and antivirus software if I can't use my computer?
It might be difficult to download tools or update your computer if your computer has a virus. In this case, you can try one of the following options:
How can I prevent infection by computer viruses?
Nothing can guarantee the security of your computer, but there's a lot you can do to help lower the chances that you'll get a virus.
It's crucial to keep your antivirus software current with the latest updates (usually called definition files) that help the tool identify and remove the latest threats.
You can continue to improve your computer's security and decrease the possibility of infection by using a firewall (US), keeping your computer up to date, maintaining a current antivirus software subscription (such as Microsoft Security Essentials), and following a few best practices. For in-depth information about how to avoid infection, visit the Microsoft Windows website.
Tip Because no security method is guaranteed, it's important to back up critical files on a regular basis.