There is a lot to be said about protecting your computer from encrypting malware. I will have more to say soon, but for now I direct you to Blaze’s Security Blog where this post covers the basics.
I use and recommend all the protection software mentioned there: WOT, No Script, ScriptSafe, Ad Block Plus, and anti-virus are all necessary on any device or computer of any make.
In addition, I recommend a cloud-based backup system, such as Carbonite. Note that Dropbox and other cloud-based sync tools are not effective in this role.