Here is a really good list of steps to help keep you safe from Ransomeware. The article is long, but stick with it and read all the headings – there are some good ideas you can easily implement. There are also some suggestions that are hard to stomach, but knowledge is power.
Personally, I use Time Capsule (network backup solution) for my Mac and it is a bummer to think that Ransomeware could find this network device and encrypt my backups too. I’ve taken to making a monthly snapshot on a USB drive for worst case recovery.