Here are few links about security on Office 365.
This covers best practices, compliance…
- Standard Response to Request for Information – Security and Privacy – http://www.microsoft.com/download/en/details.aspx?id=26647
- Security in Office 365 White Paper – http://www.microsoft.com/download/en/details.aspx?id=26552
- Cloud Computing Security Considerations – http://www.microsoft.com/download/en/details.aspx?id=1013
- Security, Privacy and Compliance Information for Microsoft Online Services – http://www.microsoft.com/online/legal/v2/?docid=21&langid=en-us