Cryptolocker and similar malware are getting more and more common. The latest versions that appeared work on also Android (one id called Simplelocker). In general what they do is to encrypt some or most of the files on your PC, tablet or smartphone, in particular text, sound, images and video files, which of course includes all your music video library.
Been a ransom, you are asked to pay some bitcoins (or similar untraceable currency) to get your files decrypted.The only defense, a part from keeping your PC clean, up-to-date, with good anti- … whatever … and being very careful on what you click and the email you open, is to keep very updated backups. Indeed once you get infected and locked / encrypted, there is absolutely nothing that you can do to decrypt the files (unless of course if you pay).
The only precaution is to have good and recent backups, and start all-over again from scratch.
But there is a very important point to remember here, not all backups are equal! Good backups are only those done on off-line media, like dvd, blu-ray disks, external usb disks that are connected only for the time of making the backup, and so on. In technical term it is often called an air-gapped backup, that is a storage that you cannot usually access from your device. This excludes most of the Clod storage and backup systems!
The reason for this is that if the backup is on a continuously or very often connected device, and the backup is done automatically as soon as new data is on your device, when the ransomware encrypts your file, the encrypted version is automatically copied on the backup device substituting the original data, and you can end up having also the backup data encrypted.
Note Added: Simplelocker is more a proof-of-concept than a real malware, in these two posts  and  Simon Bell describes the malware and how to decrypt the files.