Spyware is designed to do just that: spy on you. Spyware is a type of software that is specifically designed to gather information about your online activity.
Unlike viruses or malware, spyware doesn’t try to spread itself. Instead the goal of spyware is to get on your computer so it can gather information and present you with pop-up ads or try to redirect you to other sites.
Like adware, spyware exists in a grey area where some of it is legitimate and some of it isn’t. Like adware, the difference between legitimate and illegitimate is whether you knew about what you were getting and consented to installing it. If you didn’t consent to installing it (or consented to something else) then it’s considered malicious. Generally the term “spyware” is only used to describe illegitimate forms of this software. But because it’s such a grey area, one person’s software is another person’s spyware. Ultimately, it all depends on what you want on your system and if you chose to put it there.
Spyware can be a problem because it can interfere with your regular online activity. Between pop-up ads that it raises, attempts to redirect you to other sites, and the impact it has on your system’s performance, spyware can be a very frustrating nuisance. All the more so since systems that have spyware tend to have a lot of it. When all that spyware is running, it can make some systems practically unusable.
There are families of spyware that are known to always (or almost always) be installed through deception or as a result of a successful virus or malware attack. Security companies track these closely and build signatures into their products to help protect against installing them and remove them when they’re found. This capability is called “anti-spyware” and it’s different than traditional antivirus. In fact, simple and free antivirus packages often don’t come with anti-spyware capabilities. To help protect your system from this nuisance, you want to have a modern, full featured security software suite.