The latest danger from ransomware means that cloud backup may no longer be the best choice for keeping your data and photos safe. If Cryptolocker is released in your PC it will encrypt almost all your files. When this happens, the encryption will be synced to the files in the cloud – and therefore on to other computing devices you have synced with that cloud backup provider.
From the BBC here:
It is triggered by clicking on an exe file which means it won’t affect Apple or Linux machines. Or at least it won’t be triggered in these operating systems. However, if you are sharing, for example, a Dropbox account with all 3 operating systems then all the files in that account that are encrypted will be encrypted on all the operating systems.
In circumstances like these, using an external drive that is not connected all the time to the computer and is used to do an incremental backup daily, will be a better way to keep your invaluable files safe.