When the attachment is opened, the malware encrypts your files, so although your computer still functions normally, you can’t access your personal files.
To regain access to all of your files, you have to pay a ransom. That’s right. Ransom.
According to Chester Wisniewski, a senior security advisor at Sophos:
“It systematically hunts down every one of your personal files – documents, databases, spreadsheets, photos, videos and music collections – and encrypts them with military-grade encryption and only the crooks can open it.”
So be careful about opening email attachments. My motto? When in doubt, throw it out.