Final answer:
Programs that falsely alert you about a virus and try to make you buy software to 'fix' the issue are known as rogue security software or scareware. Hackers use these along with various methods to manipulate users and gain information or access to systems.
Step-by-step explanation:
Programs that attempt to trick you into buying software by pretending your computer is infected with a virus fall into the class of malware known as rogue security software or scareware. These malicious programs often generate alarming messages or alerts claiming that your computer is heavily infected with viruses, spyware, or other forms of malware, pressuring you into purchasing a 'full version' of the software to remove these non-existent threats. Hackers use a variety of methods to break into websites, to get people to click on links, and to lure people to give out personal information, including the deployment of such scareware.
It's important to remain vigilant and skeptical of unsolicited or unexpected security alerts, especially those that direct you to download or purchase software. Installing and regularly updating reputable antivirus and anti-malware software, from trusted vendors, can help protect your system from these types of malicious attacks.