Scareware is a type of malicious software (malware) that is designed to trick users into thinking that their computer or device is infected with malware or viruses, in order to scare them into taking certain actions, such as purchasing fake antivirus software or revealing personal information. Scareware typically presents fake pop-up alerts, warning messages, or notifications that appear to be legitimate and urgent, and often claim that the user's computer is at risk and needs immediate attention.

The main objective of scareware is to create a sense of fear, panic, or urgency in the user's mind, leading them to take hasty actions without verifying the legitimacy of the alerts. These actions can include clicking on links, downloading and installing software, entering personal or financial information, or making payments for fake or unnecessary software. Scareware can be distributed through various methods, such as malicious websites, spam emails, social engineering tactics, or even bundled with legitimate software downloads.

Scareware is a deceptive and fraudulent practice that preys on users' lack of knowledge or awareness about cybersecurity threats. It can result in financial loss, identity theft, and other security risks. Some common examples of scareware include fake antivirus software, fake system optimizers, fake registry cleaners, and fake ransomware alerts.