Adware refers to programs that are supported by advertising. In exchange for using a free program, we are presented with advertisements. Juno's basic Internet service is a good example of adware - free dial-up access to the Internet, and an advertising bar that stays on the screen as long as we are connected. With most adware, we can remove the advertising by paying a fee for the program or service.
A lot of the adware programs collect data about our web surfing habits and send that information off to a central computer while we are online. They do this in order to present you with 'targeted' ads that you are more likely to buy from. Reputable companies will spell out the fact that their ad-supported program is collecting the information, and will tell you what they are doing with it. This is usually found in the License Agreement that you agreed to when you first installed the program. (You did read that closely before you accepted it, didn't you?)
Spyware programs are similar to adware programs in that they collect the same kind of information and send it off to a central computer. The main difference is that spyware programs don't usually let us know that they are being installed when we install their host program (like iMesh or Gator), or install themselves even if we expressly click on the button that indicates we do not want to install the program! There are even 'drive-by downloads' that install the programs while you are surfing the web, simply by going to a certain page or site. (See Trojans) I once went to the iMesh site to see what it was all about, and came away with 3 new spyware programs just from the main page!
Even if we ignore the privacy aspects of programs like these, we still have a lot of potential problems when we have them on our computers. They use up memory which can slow down our computer, and they can often interfere with other programs because they have been poorly written. If a couple of spyware programs are trying to record and send information, chances are you will notice your computer running slower, and your Internet connection will seem very slow.
I have had calls from folks who try to start a word processing program, only to have it disappear after the initial logo screen. They believe that there is a problem with the program itself, and try to reinstall it several times (often at the advice of another tech that they called) in order to correct the problem. What they fail to look for is spyware running in the background, eating up their system resources and preventing the legitimate program from being able to start. By removing the spyware programs, the system has more memory available to do what it is supposed to, and everything is fine.
