What type of malware restricts access to a computer system until a fee is paid?

Ransomware is a type of malware that is specifically designed to restrict access to a computer system, often by encrypting the files within it, until a ransom fee is paid to the attacker. The mechanism usually involves displaying a message to the user, informing them that their files have been locked and providing instructions on how to pay the ransom to regain access.

This type of malware can cause significant disruptions and data loss, as victims may feel pressured to pay the ransom to recover important information, sometimes leading to no guarantee that they will actually regain access even after payment. Unlike other malware types, such as Trojan horses, spyware, or adware, ransomware's primary goal is to extort money from the victim, which is what makes it particularly concerning in the landscape of cyber threats.