Spyware
Any software that covertly gathers user information through the user's Internet connection without his or her knowledge, usually for advertising purposes. Spyware applications are typically bundled as a hidden component of freeware or shareware programs that can be downloaded from the Internet. Once installed, the spyware monitors user activity on the Internet and transmits that information in the background to someone else. ...
 

Adware
While not necessarily malware, adware is considered to go beyond the reasonable advertising that one might expect from freeware or shareware. Typically a separate program that is installed at the same time as a shareware or similar program, adware will usually continue to generate advertising even when the user is not running the origianlly desired program.
 

Virus
a software program capable of reproducing itself and usually capable of causing great harm to files or other programs on the same computer; "a true virus cannot spread to another computer without human assistance"


Trojan Horse
A Trojan horse is a program in which malicious or harmful code is contained inside apparently harmless programming or data in such a way that it can get control and do its chosen form of damage, such as ruining the file allocation table or hard disk. A Trojan horse may be widely redistributed as part of a computer virus.
 

 

 

If your computer starts to behave strangely or displays any of the symptoms listed below, you may have spyware or other unwanted software installed on your computer.

 

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I see pop-up advertisements all the time. Some unwanted software will bombard you with pop-up ads that aren't related to a particular Web site you're visiting. These ads are often for adult or other Web sites you may find objectionable. If you see pop-up ads as soon as you turn on your computer or when you're not even browsing the Web, you may have spyware or other unwanted software on your computer.

 

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My settings have changed and I can't change them back to the way they were. Some unwanted software has the ability to change your home page or search page settings. This means that the page that opens first when you start your Internet browser or the page that appears when you select "search" may be pages that you do not recognize. Even if you know how to adjust these settings, you may find that they revert back every time you restart your computer.

 

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My Web browser contains additional components that I don't remember downloading. Spyware and other unwanted software can add additional toolbars to your Web browser that you don't want or need. Even if you know how to remove these toolbars, they may return each time you restart your computer.

 

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My computer seems sluggish. Spyware and other unwanted software are not necessarily designed to be efficient. The resources these programs use to track your activities and deliver advertisements can slow down your computer and errors in the software can make your computer crash. If you notice a sudden increase in the number of times a certain program crashes, or if your computer is slower than normal at performing routine tasks, you may have spyware or other unwanted software on your machine.