Ransomware is a type of malware that encrypts a victim’s files or locks them out of their system, with attackers demanding payment (usually cryptocurrency) in exchange for restoring access. This lesson covers how ransomware typically spreads (often through phishing emails or unpatched software vulnerabilities), the significant financial and operational impact it has had on businesses and even hospitals or government systems globally, and why regular backups and updated software are among the most effective defenses against it.