Adware, often called advertising-supported software by its developers, is software that generates revenue for its developer by automatically generating online advertisements in the user interface of the software or on a screen presented to the user during the installation process. The software may generate two types of revenue: one is for the display of the advertisement and another on a "pay-per-click" basis, if the user clicks on the advertisement. Some advertisements also act as spyware, collecting and reporting data about the user, to be sold or used for targeted advertising or user profiling. The software may implement advertisements in a variety of ways, including a static box display, a banner display, full screen, a video, pop-up ad or in some other form. All forms of advertising carry health, ethical, privacy and security risks for users. The 2003 Microsoft Encyclopedia of Security and some other sources use the term "adware" differently: "any software that installs itself on your system without your knowledge and displays advertisements when the user browses the Internet", i.e., a form of malware. Some software developers offer their software free of charge, and rely on revenue from advertising to recoup their expenses and generate income. Some also offer a version of the software at a fee without advertising. Advertising-supported software In legitimate software, the advertising functions are integrated into or bundled with the program. Adware is usually seen by the developer as a way to recover development costs, and to generate revenue. In some cases, the developer may provide the software to the user free of charge or at a reduced price. The income derived from presenting advertisements to the user may allow or motivate the developer to continue to develop, maintain and upgrade the software product. The use of advertising-supported software in business is becoming increasingly popular, with a third of IT and business executives in a 2007 survey by McKinsey & Company planning to be using ad-funded software within the following two years. Advertisement-funded software is also one of the business models for open-source software. Application software Some software is offered in both an advertising-supported mode and a paid, advertisement-free mode. The latter is usually available by an online purchase of a license or registration code for the software that unlocks the mode, or the purchase and download of a separate version of the software. Some software authors offer advertising-supported versions of their software as an