Ransomware

Ransomware↗ is a type of malware↗ that encrypts a victim's files, making them completely inaccessible, and then demands payment, usually in cryptocurrency, in exchange for the decryption key needed to restore access. Increasingly, attackers also steal a copy of the data first and threaten to publish it, adding extortion pressure even for victims who have backups.

Ransomware typically spreads through phishing↗ emails, exploited vulnerabilities, or compromised remote-access credentials, and can lock up an entire organization's network within hours of the initial infection. The most effective defenses are prevention (patching, phishing awareness, restricting access) combined with tested, offline backups, since paying the ransom is never guaranteed to actually restore your data and directly funds further attacks.