WHAT IS RANSOMWARE?

LOS ANGELES— 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 are 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 users from accessing data on it until a ransom is paid, he said.

How does your computer become infected with ransomware?

In most cases, the software infects computers through links or attach- ments in malicious messages known as phishing emails.

“The age-old advice is to never click on a link in an email,” said Jerome Segura, a senior malware intelligence researcher at Malwarebytes, a San Jose-based company that has released anti-ransomware software.

How ransomware works

“Ransomware, like the name suggests, is when your files are held for ransom,” said Peter Reiher, an adjunct professor at UCLA who specializes in computer science and cybersecurity. “It finds all of your files and encrypts them and then leaves you a message. If you want to decrypt them, you have to pay.”

How to avoid these attacks

The first step is being cautious, experts say. But Villasenor said there is “no perfect solution” to the problem.

Users should regularly back up their data and ensure that security updates are installed on your computer as soon as they are released.