Spyware is a term that has come to describe a variety of undesirable software, ranging from annoying pop-up ads to programs that surreptitiously send your private information to other people. Indications of common spyware infections include the following:
Unexpected new toolbars, favorites, and links in your web browser
Changes to your browser’s home page and default search provider
Numerous pop-up ads
Sudden occurrence of computer crashes or slow performance
Note that spyware doesn’t necessarily "spy" on you. A common characteristic of anything dubbed "spyware" is that it does its deeds—malicious or otherwise—without your informed consent. (Spyware typically gets installed by deceitfully asking permission to ...