Signs Your Computer has a Virus

The Internet seems to be full of good guys and bad guys, and the bad guys want to take over your computer. That might seem to be an oversimplification, but the fact is that there are thousands of viruses, malware, or trojanware that could infect your system. Sometimes getting infected is as easy as visiting a website that is on an infected server.

So how do you know if your system is infected? Basically, you need to be aware of how your uninfected system normally works and pay attention to anything that changes. Here are a few things that may signal you have an infection. (These are listed in no particular order.)

• Your browser's homepage changes, without any action on your part.
• The default search engine used by your browser inexplicably changes.
• Unfamiliar tools or toolbars appear in your browser window.
• You are routinely redirected to websites you did not intend to visit.
• Popups start routinely appearing that have nothing to do with the website you are visiting.
• Your browser refuses to open security-related websites or Microsoft websites.
• Your browser slows down quite a bit or hangs. (Over long periods of time, such as a couple of days. Short slowdowns could be related to transient communications issues over the Internet.)

Of course, virus infection doesn't just exhibit itself in your browser. You may also notice some behavior changes even when your browser is not running. Here are a few things you may notice:

• Your virus checker or other security software starts issuing warnings.
• Your virus checker or other security software stops working.
• Windows starts displaying unexpected or excessive error messages.
• You notice excessive Internet activity, especially when you are not using your browser.
• You notice excessive hard drive activity, especially when coupled with Internet activity.
• Your system seems to use excessive CPU or memory. (You can check this by using the Task Manager.)
• Your system seems to be working on background tasks that you don't control.
• Programs begin automatically when you did nothing to enable such behavior.
• You can no longer start Task Manager, Registry Editor, or open a command-prompt window.
• You notice in the Control Panel that software has been installed on your system and you didn't do it.
• New icons appear on your desktop that you didn't install.

If you have a virus or other malware on your system, you'll typically notice multiple indicators from the above lists, not just one or two. If you begin to believe that you have an infection, contact a local computer repair shop and see if they can check your system. (That is normally the easiest path to an infection-free system.)

 This tip (13306) applies to Windows 7 and 8.