Always consider security issues carefully when your data contains sensitive information such as identification and health information.
Cloud based storage and synchronizing service
Use this option only when there is no sensitive information in the data set. A good strategy is to keep multiple copies of the back-ups using both a cloud based storage service and local hard drive.
Consider these tools to encrypt your data files.
(Mac buildin, Free)
OS X buildin application. The icon is a screen shot of part of its interface.
An on-the-fly encryption tool. Once installed, files will automatically be decrypted when accessed, and encrypted when you no longer in use.
Can be used as a lightweight encryption tool. Suitable for encrypting documents.
Integrate with Windows shell. Provider right-click encryption/decryption functionality.