Adware and Spyware are two types of software which can get installed on your computer without your knowledge, and whose activities intrude into your use of the computer and also your privacy. Unlike computer viruses, adware and spyware generally do not try to cause damage to your computer system or try to spread themselves to other computers.
- unwanted advertising matter randomly appearing on your screen
- your browser's home page being "hijacked" to display a page for some commercial service or search engine
- problems connecting to web services which authorise access on the basis of internet IP address
Some free or shareware software (for example the Opera web browser) legitimately displays advertising in a clearly stated way to finance the software's development. However, adware does this in a covert way by installing itself secretly, for example by including itself alongside some other product you are installing, or by enticing you to click on a web-screen image. In some cases, you may unwittingly agree to adware installation in the small print of an on-screen licence agreement when installing a software package.
As well as displaying advertising, adware can also record information about your web-browsing activities and report these to a third party, for example to target the advertising to your interests. Some web browser add-ons, such as the Alexa toolbar, do this.
Not all unwanted screen advertising is a result of adware. Some web pages produce their own local onscreen pop-ups when you view them. These pop-ups can be irritating but are not produced by an adware infection. They can usually be supressed by a "pop-up stopper" such as the one provided by the Google Toolbar.
Another form of intrusive screen pop-up on Windows PCs makes use of Microsoft's Messenger Services (note that this is different from MSN Instant Messenger) and has Messenger Service in the pop-up title-bar. In earlier versions of Windows, this facility was called WinPopup. For information on disabling Messenger Services or WinPopup see, for example, http://www.opentechsupport.net/forum/internet-guides/11211-how-disable-messenger-services.html
Whereas adware may be largely an irritation, spyware presents a much more serious threat. Spyware snoops on your computer activity and may record keystrokes, including passwords and other private information, which are then communicated to others, possibly resulting in criminal activity such as using your credit card details. Spyware installation, too, may originate as part of a freeware product, or by enticing you to click on a web-screen image.