A screen locker is a type of malicious software that restricts access to a computer or mobile device by locking its screen. Victims are typically unable to use their device or access files until they meet certain demands, often paying a ransom to the attacker. Screen lockers are commonly used in ransomware attacks, displaying a message or warning that claims to be from law enforcement or another authority. Unlike more advanced ransomware, screen lockers usually do not encrypt files but instead prevent interaction with the operating system. They often exploit social engineering tactics to scare or pressure victims into complying with the demands.