Ransomware
Malicious software that locks your files and demands payment to release them.
Ransomware is malicious software that locks or encrypts your files and then demands payment for their release. It typically arrives through a booby-trapped email attachment or link, a fake download, or a poisoned advert, and once it runs it can spread across a device or network, leaving a ransom note behind. Victims range from individuals to hospitals and businesses, and paying is discouraged: it funds further crime and offers no guarantee the criminals will actually restore your data.
The most effective protection is preparation rather than cure. Keep regular backups of anything important, ideally with a copy kept offline or otherwise disconnected, so you can recover without negotiating. Keep software and operating systems updated to close the flaws these attacks exploit, be cautious with unexpected attachments and links, and use reputable security tools. If you are hit, disconnect the device from networks to limit the spread, and seek advice before considering any payment. In the UK, the National Cyber Security Centre publishes practical guidance, and an attack can be reported to Action Fraud (England, Wales and Northern Ireland) or Police Scotland on 101. Much ransomware still begins with ordinary phishing.