Scareware is several classes of software, often with limited or no benefit, that are sold to consumers by certain unethical marketing practices. The selling approach is designed to cause shock, anxiety, or threats, generally directed at an unsuspecting user. Some forms of spyware and adware also use scareware tactics. A frequently used tactic is to convince users that their computer is infected with a virus, then suggest that they download, and pay for, anti-virus software to remove it. Usually the virus is entirely fictional and the software is non-functional or malware.


Source : Wikipedia