Spyware is a general term used to describe a computer software that is installed surreptitiously on a personal computer that performs certain behaviors such as to intercept or take partial control over the user's interaction with the computer, without the user's knowledge or permission.

Spyware software are mainly bundled as a hidden component of free software or shareware applications that we download from the Internet. Many free software applications that are available on the Internet contain spyware and users should always be causios about this when downloading such software on their system.

Spyware is considered a malicious software and can be treated similar to a Trojan Horse Virus in that users unknowingly install the spyware when they install some free software. And the most common way users computer gets infected with spyware is through free peer-to-peer file sharing software like Kazaa p2p software.                        

As the term spyware means spying software that monitors the computer user's Internet behavior secretly, the functions of spyware go beyond usual computer monitoring. Spyware software collects various types of computer information and personal information, such as Internet browsing habit, websites that have been visited by the user, and some times spyware can take control of the users computer to install more malware software's which can redirect users Internet Web browser to unwanted websites which may download more harmful Trojans and viruses. Spyware software's are also used to show advertisement about fake antivirus software, which installs trojans that changes users computer settings, resulting in slow computer performance, slow Internet connection speeds, browser hompage changes and damages files on computer.