LOS ANGELES (AP) — Computers across the world were locked up and users' files held for ransom when dozens of countries were hit in a cyber-extortion attack that targeted hospitals, companies and government agencies.

Here's a look at how malware and ransomware work and what people can do if they fall victim to attacks.

WHAT IS MALWARE AND RANSOMWARE?

Malware is a general term that refers to software that's harmful to your computer, said John Villasenor, a professor at the University of California, Los Angeles. Ransomware is a type of malware that essentially takes over a computer and prevents u...