Spyware is often installed as part of a 3rd party software package, without the users knowledge. Once installed, the software then proceeds to gather information about the users browsing habits and can sometimes monitor and track other personal information. Spyware has now become a broad term for any software operating without the users consent, which somehow benefits a 3rd party. Some direct effects include:
Many systems are infected with Spyware/Adware without being noticed and attempts to remove the software is often difficult to achieve for the average user. The companies that distribute Spyware software often claim that the end user agreed to this monitoring whilst installing a certain software application (often browser toolbars and extensions). However, large and complex user agreements distort the real actions of the spyware.
Microsoft Windows and the Internet Explorer browser are the primary targets for Spyware, simply because they are the software of choice for the majority of people. Using an alternative operating system or browser may help reduce the risk of spyware, but only because it is less common (not necessarily because it is more secure). Downloading and running applications from the internet is the most popular route of infection, however browser exploits and some viruses may also install spyware components.
If you find that you have unwanted advertisements appearing whilst you are using your computer (often gambling or pornography related) or unwanted toolbars in your browser, the chances are you have some form of spyware infection.
This malicious use of a PC with spyware is frowned upon, however an extremely profitable business for a select few. Website owners can be paid as much as $0.50 per install of an ActiveX control containing Spyware, which makes this attractive to nefarious sites such as illegal/cracking/hacking/pornographic website's.
Once users have been educated that they must take sensible precautions when using the internet and downloading software, it is often straight forward to remove the Spyware threat with the correct tools. A recent trend is for some Spyware products to distribute themselves as Spyware Removal Tools - which of course can be extremely harmful. It is important to combine effective Anti-Spyware tools with other Anti-Virus and Firewall applications for all round PC protection. - a single application will not protect from all 3 threats.