The Looming Issue with Email Sharing

If you’ve been following my suggestions in this series, then your SaaS sharing configuration now protects sensitive information and your IaaS/PaaS access controls accurately follow the principle of least privilege. Of course, that doesn’t mean you’re done! We must now tame the giant of all file-sharing beasts: email. An email is probably the worst way to share files because there’s no way to limit who sees the file after it is sent. When you email an attachment to somebody, you’ve lost control of it. Even though some form of control over file sharing will always be necessary, don’t tighten your SaaS settings so much that you force people to go around your controls and pick email.

It comes back to this idea of balancing risk and utility. Make it easy for your users to request when they need to share something externally, and then monitor how that permission is used and nudge users toward good behaviors. This could be as simple as a self-service mechanism, an automated help desk support system or even a bot assistant that provides automatic coaching prompts to guide users to approved applications. Whatever it is, the barrier to receiving permission to share something externally should be low and justifiable to the business.

Control beyond the cloud: EDRM

Even if all the permissions are correct—there’s a business justification for sharing a file and the controls have been configured appropriately so that only authorized users have access—once an authorized user downloads the file, the organization can lose control of sensitive information once again. Alice receives access to a sensitive file stored in Salesforce and makes a local copy. Bob would like one, too, but his Salesforce permissions don’t allow it. What’s to prevent Alice from forwarding it to Bob in an email message or a Slack conversation? Nothing. After all, it’s a local copy—it isn’t under the control of the cloud.

This is where enterprise digital rights management (EDRM) becomes a part of your security strategy. EDRM places a wrapper around the file. The wrapper encrypts the contents and appends an access control list right into the file itself. When an authorized user accesses the file, they must first supply their credentials. To continue our example, Alice’s company applies EDRM to all W2 forms. After Alice downloads and tries to open one, the EDRM system checks whether Alice is on the access control list—and if she is, her computer will display a decrypted version of the file and enforce any other restrictions (such as no-save-as, no-print, etc.).

It’s still a file, though, meaning Alice can do file-type stuff like forwarding a copy to Bob, which she does. Bob has no legitimate business need to see W2 forms and is therefore not included in the access control list appended to the file. When Bob attempts to open the copy, the EDRM system checks whether he’s on the access control list. Because he isn’t, we can predict what’s next: Bob’s computer refuses to open the file and displays an error message indicating insufficient permission.

Note that the file is never stored on disk in clear-text. Protected files contain only wrappers and encrypted data. The EDRM system displays decrypted contents only after authorized users have authenticated, but the data in storage remains encrypted. EDRM allows organizations to retain control over their sensitive information even when the sensitive information is no longer visible to the cloud.

Don’t shirk shared responsibility in the cloud

No one wants to appear in the news because a simple cloud setting unintentionally led to sensitive files gracing the fingertips of the wrong people. Solving the bigger problem of cloud applications breached from misconfigurations starts by assessing how people need to exchange information and with whom. The next step is establishing a governance program that facilitates safe sharing, mediated by security tools that detect and mitigate common sharing risks in the course of everyday business operations.

This article was originally published on Forbes Tech Council