I bought an external hard drive at Costco and back up my files about once a week. I've actually had to use those backed up files when an "update" didn't work properly and had to reinstall, using the old files on the external.

You can set your computer to back up automatically.

You can go to the website of Dropbox https://www.dropbox.com or Mimedia http://www.mimedia.com/

and install them. You get a certain amount of storage for free, or if you need more you can pay. The free is plenty for me.

Once they are installed, when you add a file to your computer it automatically backs it up. Also, you can put them on more than one computer and you can access the files from either computer.

When my computer totally died, I got a new computer, installed the software and had all my files back. I have done this a few times now. Or even if your old computer has not died, you can easily transfer all your files to a new one.

Unlike an external hard drive, you don't have to remember to back up your files, it is done automatically.

The problem with the sites that automatically back up your files is that they will back up the new "changed" file (overwriting the original) which would be the locked one (if you had this virus). I use carbonite and they claim to keep old copies of files for 3 months but I take no chances. I use smugmug to back up my photos and have an external drive that I keep disconnected when I'm not using it for everything else that I don't want to lose. I just add any new files to the external every few days.