Many sites that you might visit on the Internet, and also some software that you install, will install tracking software on your computer called "adware" or "spyware." These are hidden programs that track your internet usage, usually for advertiser research, but can also steal your personal information, interfere with the operation of your computer and may even damage your data.
Resist installing free software from pop-ups, such as the programs that show weather forecasts on your desktop or smiley faces in your email. These programs are often spyware/adware and/or install spyware/adware on your computer.
There are many free programs available that prevent and/or detect spyware/adware:
For more information, visit the Microsoft Computer Security webpage.