Spyware is computer software that is installed in a secret manner on your computer to collect information about you, your computer or browsing habits without your informed consent.
While the term spyware suggests software that secretly monitors your behavior, the functions of spyware extend well beyond simple monitoring. Spyware programs can collect various types of personal information, such as Internet surfing habits and sites that have been visited, but can also interfere with your control of the computer in other ways, such as installing additional software and redirecting Web browser activity. Spyware is known to change computer settings, resulting in slow connection speeds, different home pages, and/or loss of Internet or functionality of other programs.
In other words loss of your productivity...
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