Its not Dropbox's Concern – IT'S YOURS!
Dropbox is a business ready cloud sharing solution with some great security features to protect your data at rest. When it comes to securing how data stored in Dropbox is accessed and shared, however, Dropbox expects the customer to take responsibility for security. The first security step to consider is using a single sign-on solution (SSO) to authenticate your users. But even with SSO in place, there still remain vulnerabilities because username and password protection does not prevent user error, malicious insider activity, or hacker-compromised credentials.
To learn more about how you can secure Dropbox usage, please read the Dropbox whitepaper.