Google has invested heavily into security, and by our estimates, they are among the leading companies in offering consumers and organizations robust tools to ensure their data is secure. Small and large companies and governments now trust and rely on Google for their most valuable data. We highly recommend everyone uses Google’s optional (and free) 2-Step Verification feature. You can read more here: https://www.google.com/landing/2step/ 

Google doesn't use your Drive, Gmail, or Photos to show you personalized ads, but you should familiarize yourself with Google's privacy policy to understand how they access and user your data. https://policies.google.com/privacy?hl=en

We also support bank data feeds to Microsoft Excel workbooks, which offers Tiller customers another choice in their spreadsheet tool. When used with desktop Excel, this will allow customers the flexibility of keeping their spreadsheets outside of the cloud.

Read more about Tiller's security