While the term spyware suggests software that secretly monitors the user's behavior, the functions of spyware extend well beyond simple monitoring. Spyware programs can collect various types of personal information, such as Internet surfing habit, sites that have been visited, but can also interfere with user control of the computer in other ways, such as installing additional software, redirecting Web browser activity, accessing websites blindly that will cause more harmful viruses, or diverting advertising revenue to a third party. Spyware can even change computer settings, resulting in slow connection speeds, different home pages, and loss of Internet or other programs. In an attempt to increase the understanding of spyware, a more formal classification of its included software types is captured under the term privacy-invasive software.
In response to the emergence of spyware, a small industry has sprung up dealing in anti-spyware software. Running anti-spyware software has become a widely recognized element of computer security best practices for Microsoft Windows desktop computers. A number of jurisdictions have passed anti-spyware laws, which usually target any software that is surreptitiously installed to control a user's computer.
The term adware frequently refers to any software which displays advertisements, whether or not the user has consented. Programs such as the Eudora mail client display advertisements as an alternative to shareware registration fees. These classify as "adware" in the sense of advertising-supported software, but not as spyware. Adware in this form does not operate surreptitiously or mislead the user, and provides the user with a specific service.
Most adware is spyware in a different sense than "advertising-supported software," for a different reason: it displays advertisements related to what it finds from spying on you. Claria Corporation's Gator Software and Exact Advertising's BargainBuddy are examples. Visited Web sites frequently install Gator on client machines in a surreptitious manner, and it directs revenue to the installing site and to Claria by displaying advertisements to the user. The user receives many pop-up advertisements.
Other spyware behavior, such as reporting on websites the user visits, occurs in the background. The data is used for "targeted" advertisement impressions. The prevalence of spyware has cast suspicion upon other programs that track Web browsing, even for statistical or research purposes. Some observers describe the Alexa Toolbar, an Internet Explorer plug-in published by Amazon.com, as spyware, and some anti-spyware programs such as Ad-Aware report it as such. Many of these adware distributing companies are backed by millions of dollars of adware-generating revenues. Adware and spyware are similar to viruses in that they can be malicious in nature. However, people are now profiting from these threats, making them more and more popular.
Similarly, software bundled with free, advertising-supported programs such as P2P act as spyware, (and if removed disable the 'parent' program) yet people are willing to download it. This presents a dilemma for proprietors of anti-spyware products whose removal tools may inadvertently disable wanted programs. For example, recent test results show that bundled software (WhenUSave) is ignored by popular anti-spyware program Ad-Aware, (but removed as spyware by most scanners) because it is part of the popular (but recently decommissioned) eDonkey client. To address this dilemma, the Anti-Spyware Coalition has been working on building consensus within the anti-spyware industry as to what is and isn't acceptable software behavior. To accomplish their goal, this group of anti-spyware companies, academics, and consumer groups have collectively published a series of documents including a definition of spyware, risk model, and best practices document.
