As a society, we expect advertising. We are used to the idea that advertising provides a source of revenue for businesses that would otherwise find it difficult to charge for their service or content, keeping television, radio and the Internet available and mostly affordable for the average citizen.

Ads have become an essential part of the Internet economy, and will likely stay that way for the foreseeable future. As such, it is important, at least for the health of some sections of the software industry, to make the distinction between spyware and ad-supported software.

Again, as stated in the section above, there are no official or legal definitions of these types of software, but as a generally accepted guideline, ad-supported software can be defined as a freely available product that is funded by advertising.

Of course, this means the entire Internet is essentially ad-supported software, but I digress… ad-supported software products will inform you prior to installation that advertising is part of the provided package, and that information may be transmitted from your computer to aid in targeting these adverts, allowing you to make an informed choice.

Ad-supported software is a major source of revenue for many smaller software companies, and can provide consumers with economical alternatives to costly software. A good example of ad-supported software is the 'sponsored mode' of the popular Eudora mail client. Note the presence of advertising is clearly stated.

Ad-supported software can be an excellent way for small companies to market their products provided they are upfront with their methods. The point at which spyware branches off from ad-supported software is when the software does not clearly state its intended purpose.

Spyware is a blanket term that covers all kinds of generally unhelpful software, from tools that enable companies to deliver ads to you based on your surfing habits, to programs that attempt to hijack your browser settings, all the way to software designed to steal ad-revenue from legitimate online businesses by covering or replacing their adds. Here's a brief guide to some of the categories of nastiness that you may see.

Adware: The most common form of spyware, these are programs which will observe your surfing habits, then report them to one or more servers on the Internet who will then tailor advertising content to your preferences and deliver it to your computer through pop-ups or other methods. Adware is generally bundled in with various freeware applications to help the producers defray the costs, or in some cases, bundled with software produced by the same company, where the license to use the software hinges on the users' acceptance of the adware working in the background. Examples of adware applications include Gator and Doubleclick.

Almost all major peer-to-peer file-sharing programs, such as Kazaa Media Desktop, contain adware. There is a fine line between adware and ad-supported software, and it's generally at the point where you decide the loss of privacy is worth the value of the product you are being offered. In many cases, the products are being marketed towards novice computer users, under the obvious assumption that they will not realize the functionality of the software can be found in other products without unnecessary adware bundled in. This possible exploitation of the unwary, and the idea that some companies involved do not necessarily reveal the extent of the information they are harvesting or the uses to which they intend to put it, tilts the scales.

Be aware that using some of the methods detailed later on to block or remove adware can violate the license agreement of the programs it was included with. This is true in the case of the Gator Corporation's software such as Ewallet and Weatherscope, and also with Kazaa Media Desktop.