Spyware consists of small spy programs that may be installed on your PC, reporting on your movements on the Internet. They run in the background without your knowledge. Different spyware programs have different objectives, but they typically gather information about your interests and movements on the Internet for advertising purposes.
Installed via freeware or viruses
In most cases, you will have allowed the spies to enter your system yourself. This happens, for instance, if you install freeware, in which case you may unwittingly install spyware on your PC. Spyware can also install itself via a virus.
Spyware checker
It is a good idea to install a dedicated spyware checker. There are several programs on the market; one of them is Ad-Aware. Ad-Aware works like antivirus software – only it checks for spyware instead of for viruses.