Spyware :: Threats :: Adware
Adware is advertising supported software. This software displays adverts while the software is running. Typically the developer forms an agreement with a 3rd party company to manage displaying adverts within their software. This 3rd party also has agreements with some or many other companies wanting to advertise their product or service. So once the developer accepts, they may need to insert some code supplied by the advertising company which delivers the ads. The adverts are normally in the form of a pop-up windows or banner ads.
There are many advertising companies about, the most popular being Cydoor and Radiate. Adware is considered by many to be a good method of making software freely to a public, however is has been criticised because there are concerns about exactly what information is sent about end user to the advertising companies. This is why there can be a fine line between adware and spyware, and people often mix up the two. While many will agree that is fair enough that adverts are displayed because the software was free to them anyway (many adwares also offer a ad-free version for a price) some are concerned about the way the adware is installed. Sometimes the advertising component is separate from the developers software, but are installed together. This could mean that the adverts are continually popping up even if the developers software (adware) is not even running. Even more worrying is the fact that some adware when uninstalled don't uninstall the advertising component along with it, meaning that the adverts may keep appearing endlessly, and may take an experienced computer user to get rid of the adware fully.